Antigenic polymorphism of the T4 differentiation antigen expressed on human T helper/inducer lymphocytes

Inherited OKT4 epitope deficiency in a Chinese rhesus macaque

OKT4 is an important epitope of the CD4 molecular. Amino acid mutations in the CD4V3 region result in deficiency of the OKT4 epitope in human. Here, we firstly reported a case of hereditary deficiency of OKT4 epitope in an inbred Chinese rhesus macaque family. This epitope deficiency is due to cytosine to thymine transition and homozygote at the nucleotide position 793 of CD4 coding sequences, which leads to the replace of arginine at 265th position of CD4 molecule by tryptophan. The results reveal that OKT4 epitope deficiency is a very old phenotype and may be parentally inherited, and emphasize the importance of avoiding inbreeding in primate population breeding.

Complete Multilineage CD4 Expression Defect Associated With Warts Due to an Inherited Homozygous CD4 Gene Mutation

Idiopathic T-CD4 lymphocytopenia (ICL) is a rare and heterogeneous syndrome characterized by opportunistic infections due to reduced CD4 T-lymphocytes (<300 cells/μl or <20% T-cells) in the absence of HIV infection and other primary causes of lymphopenia. Molecular testing of ICL has revealed defects in genes not specific to CD4 T-cells, with pleiotropic effects on other cell types. Here we report for the first time an absolute CD4 lymphocytopenia (<0.01 CD4⁺ T-cells/μl) due to an autosomal recessive CD4 gene mutation that completely abrogates CD4 protein expression on the surface membrane of T-cells, monocytes, and dendritic cells. A 45-year-old female born to consanguineous parents consulted because of exuberant, relapsing, and treatment-refractory warts on her hands and feet since the age of 10 years, in the absence of other recurrent infections or symptoms. Serological studies were negative for severe infections, including HIV 1/2, HTLV-1, and syphilis, but positive for CMV and EBV. Blood analysis showed the absence of CD4⁺ T-cells (<0.01%) with repeatedly increased counts of B-cells, naïve CD8⁺ T-lymphocytes, and particularly, CD4/CD8 double-negative (DN) TCRαβ⁺ TCRγδ^- T-cells (30% of T-cells; 400 cells/μl). Flow cytometric staining of CD4 using monoclonal antibodies directed against five different epitopes, located in two different domains of the protein, confirmed no cell surface membrane or intracytoplasmic expression of CD4 on T-cells, monocytes, and dendritic cells but normal soluble CD4 plasma levels. DN T-cells showed a phenotypic and functional profile similar to normal CD4⁺ T-cells as regards expression of maturation markers, T-helper and T-regulatory chemokine receptors, TCRvβ repertoire, and in vitro cytokine production against polyclonal and antigen-specific stimuli. Sequencing of the CD4 gene revealed a homozygous (splicing) mutation affecting the last bp on intron 7-8, leading to deletion of the juxtamembrane and intracellular domains of the protein and complete abrogation of CD4 expression on the cell membrane. These findings support previous studies in CD4 KO mice suggesting that surrogate DN helper and regulatory T-cells capable of supporting antigen-specific immune responses are produced in the absence of CD4 signaling and point out the need for better understanding the role of CD4 on thymic selection and the immune response.

CD4 receptor diversity in chimpanzees protects against SIV infection

Human and simian immunodeficiency viruses (HIV/SIVs) use CD4 as the primary receptor to enter target cells. Here, we show that the chimpanzee CD4 is highly polymorphic, with nine coding variants present in wild populations, and that this diversity interferes with SIV envelope (Env)-CD4 interactions. Testing the replication fitness of SIVcpz strains in CD4+ T cells from captive chimpanzees, we found that certain viruses were unable to infect cells from certain hosts. These differences were recapitulated in CD4 transfection assays, which revealed a strong association between CD4 genotypes and SIVcpz infection phenotypes. The most striking differences were observed for three substitutions (Q25R, Q40R, and P68T), with P68T generating a second N-linked glycosylation site (N66) in addition to an invariant N32 encoded by all chimpanzee CD4 alleles. In silico modeling and site-directed mutagenesis identified charged residues at the CD4-Env interface and clashes between CD4- and Env-encoded glycans as mechanisms of inhibition. CD4 polymorphisms also reduced Env-mediated cell entry of monkey SIVs, which was dependent on at least one D1 domain glycan. CD4 allele frequencies varied among wild chimpanzees, with high diversity in all but the western subspecies, which appeared to have undergone a selective sweep. One allele was associated with lower SIVcpz prevalence rates in the wild. These results indicate that substitutions in the D1 domain of the chimpanzee CD4 can prevent SIV cell entry. Although some SIVcpz strains have adapted to utilize these variants, CD4 diversity is maintained, protecting chimpanzees against infection with SIVcpz and other SIVs to which they are exposed.

Effects of Sensitization to Dinitrochlorobenzene (DNCB) on Clinical Pathology Parameters and Mitogen-Mediated Blastogenesis in Cynomolgus Monkeys (Macaca, fascicularis)

Immunotoxicologic testing of drug candidates and environmental contaminants is of growing importance. Cutaneous delayed type hypersensitivity (DTH) is a convenient way of testing immune function in vivo. However, DTH testing must not interfere with interpretation of other relevant parameters. We have evaluated the effects of sensitization and challenge with dinitrochlorobenzene (DNCB) on clinical parameters routinely evaluated in toxicity testing and on lectin-mediated blastogenesis. Female cynomolgus monkeys were sensitized to DNCB with 4 daily applications of DNCB in acetone to the skin of the axilla. Fifteen days later, the monkeys were challenged for DTH by applying DNCB to the antecubital skin. Skin fold thickness was measured and the macroscopic appearance of the challenge site was scored 24 and 48 hr after challenge. All 5 monkeys were successfully sensitized to DNCB. There was a significant increase in the mean skin fold thickness (compared to pre-challenge thickness) of 2 mm at 24 hr and 1 mm at 48 hr ( p < 0.001). The clinical score of the challenge site was also increased. Histologic examination of the sensitization and challenge sites from a second group of monkeys exposed to DNCB in an identical manner showed the perivascular inflammatory cell infiltrate typical of DTH. Evaluation of hematologic parameters at days 7, 14, and 21 revealed no change in the erythron at any interval and a mild decrease in total WBC, neutrophil and lymphocyte counts on day 7 in 4/5 monkeys. The WBC parameters remained within the normal range and returned to pre-sensitization values at the later intervals. Clinical biochemical parameters related to liver and kidney function were evaluated at the same intervals and no changes were found. The blastogenic response of peripheral blood leukocytes to concanavalin A, phytohemagglutinin and pokeweed mitogen was mildly but not significantly decreased at day 7 but not on day 14 or 21. This study has shown that sensitization to DNCB in cynomolgus monkeys is a reliable means of evoking a DTH response which is quantifiable. It has also shown that sensitization and challenge with DNCB can be incorporated into toxicity studies without confounding interpretation of other toxicity data.

The CD4 C868T Polymorphism and Its Correlation with HIV-1 Infection in a Chinese Population

Previous studies performed in Kenya have suggested that the C868T single nucleotide polymorphism (SNP) in CD4 increases the risk of HIV-1 acquisition; however, no relevant study has been conducted in China. To evaluate the influence of this SNP on risk of HIV-1 infection in a Chinese population, the CD4 genotype was determined by DNA sequencing in 101 HIV-1 patients and 102 healthy controls. No significant differences in the genotype and allele distributions of this polymorphism were observed among the patient and control groups. Additionally, binary logistic regression analyses adjusted by age and gender revealed that the C868T polymorphism was not associated with risk of HIV-1 infection. Furthermore, when analyses of genotype and allele frequencies were stratified by gender, similar nonsignificant results were found. Our study demonstrates a null association between the CD4 C868T polymorphism and an individual's susceptibility of HIV-1 acquisition in a Chinese population. Further studies are warranted to confirm these results.

CD4+ T cells contain early extrapulmonary tuberculosis (TB) dissemination and rapid TB progression and sustain multieffector functions of CD8+ T and CD3- lymphocytes: mechanisms of CD4+ T cell immunity

The possibility that CD4(+) T cells can act as "innate-like" cells to contain very early Mycobacterium tuberculosis dissemination and function as master helpers to sustain multiple effector functions of CD8(+) T cells and CD3(-) lymphocytes during development of adaptive immunity against primary tuberculosis (TB) has not been demonstrated. We showed that pulmonary M. tuberculosis infection of CD4-depleted macaques surprisingly led to very early extrapulmonary M. tuberculosis dissemination, whereas CD4 deficiency clearly resulted in rapid TB progression. CD4 depletion during M. tuberculosis infection revealed the ability of CD8(+) T cells to compensate and rapidly differentiate to Th17-like/Th1-like and cytotoxic-like effectors, but these effector functions were subsequently unsustainable due to CD4 deficiency. Whereas CD3(-) non-T lymphocytes in the presence of CD4(+) T cells developed predominant Th22-like and NK-like (perforin production) responses to M. tuberculosis infection, CD4 depletion abrogated these Th22-/NK-like effector functions and favored IL-17 production by CD3(-) lymphocytes. CD4-depleted macaques exhibited no or few pulmonary T effector cells constitutively producing IFN-γ, TNF-α, IL-17, IL-22, and perforin at the endpoint of more severe TB, but they presented pulmonary IL-4(+) T effectors. TB granulomas in CD4-depleted macaques contained fewer IL-22(+) and perforin(+) cells despite the presence of IL-17(+) and IL-4(+) cells. These results implicate a previously unknown innate-like ability of CD4(+) T cells to contain extrapulmonary M. tuberculosis dissemination at very early stage. Data also suggest that CD4(+) T cells are required to sustain multiple effector functions of CD8(+) T cells and CD3(-) lymphocytes and to prevent rapid TB progression during M. tuberculosis infection of nonhuman primates.

Infant CD4 C868T polymorphism is associated with increased human immunodeficiency virus (HIV-1) acquisition

The C868T single nucleotide polymorphism (SNP) in the CD4 receptor encodes an amino acid change that could alter its structure and influence human immunodeficiency virus (HIV-1) infection risk. HIV-1-infected pregnant women in Nairobi were followed with their infants for 1 year postpartum. Among 131 infants, those with the 868T allele were more likely than wild-type infants to acquire HIV-1 overall [hazard ratio (HR) = 1.92, 95% confidence interval (CI) 1.05, 3.50, P = 0.03; adjusted HR = 2.03, 95% CI 1.03, 3.98, P = 0.04], after adjusting for maternal viral load. This SNP (an allele frequency of approximately 15% in our cohort) was associated with increased susceptibility to mother-to-child HIV-1 transmission, consistent with a previous study on this polymorphism among Nairobi sex workers.

Humanized IgG1 and IgG4 anti-CD4 monoclonal antibodies: effects on lymphocytes in the blood, lymph nodes, and renal allografts in cynomolgus monkeys

BACKGROUND

Optimizing therapeutic monoclonal antibody (mAb) depends on the incorporation of the necessary effector functions and the development of hypoantigenic "humanized" antibodies by genetic engineering, which then need to be tested in appropriate preclinical trials.

METHODS

Constructs of humanized OKT4A containing the complementarity-determining region (CDR) of murine OKT4A and the framework and constant regions of human light (kappa) and heavy chains (IgG1 and IgG4) were prepared and tested in cynomolgus monkeys who received a renal allograft. A prophylactic course of CDR-OKT4A/human (h) IgG1 or CDR-OKT4A/ hIgG4, either as high-dose single bolus (10 mg/kg) or as low-dose multiple infusion (1 mg/kg for 12 days) was given, and the effects on graft survival, immunohistology, circulating cells, and lymph node cells were assessed.

RESULTS

The IgG1 isotype induced coating of T cells, modulation of surface CD4 molecules, and profound depletion of CD4+ lymphocytes in peripheral blood, which persisted as long as the animals were followed (up to 7 weeks). The IgG4 isotype induced only cell coating without cell clearance or modulation. In lymph nodes, coating of lymphocytes (approximately 60%) was seen with both isotypes in the earliest sample (6 hr). After 2 days, significant depletion of lymph node CD4 cells was evident, with a decrease in the CD4 to CD8 ratio in the IgG1-treated group; no depletion occurred in the IgG4 group. The emigration of CD4+ cells into the allograft was significantly delayed in the CDR-OKT4A/hIgG1-treated animals when compared with the CDR-OKT4A/hIgG4 group as judged by immunocytochemistry (23.8+/-13.2 days vs. 7.4+/-1.5 days, P<0.001) or interleukin-2-promoted T-cell outgrowth from allograft biopsies (22.2+/-11.0 days vs. 6.3+/-0.5 days, P<0.01).

CONCLUSIONS

This study demonstrates that the in vivo effects of CDR-grafted OKT4A are dependent on its isotype. The depleting mAb CDR-OKT4A/hIgG1 significantly delays the entry of CD4+ cells into the graft, inhibiting the early phase of rejection. However, graft rejection occurs when CD4+ cells eventually infiltrate the graft, even in the presence of depressed levels of circulating CD4+ cells. Both isotypes demonstrated therapeutic efficacy: graft survival was prolonged over controls. In the case of CDR-OKT4A/hIgG4, neither lymphocyte depletion, antigenic modulation, nor prevention of infiltration is necessary for a beneficial effect, which indicates that this mAb blocks CD4 function or renders the CD4+ cell less responsive. The lack of depletion is a feature of potential clinical advantage in minimizing the risk of excessive immunosuppression.

Differential binding of two monoclonal antibodies directed against the chicken CD8 alpha molecule

Two murine monoclonal antibodies (mAb), CT8 and AV14, have been shown to recognise the avian homologue of the mammalian CD8 alpha molecule. In previous flow cytometry studies we could discriminate two subpopulations of CD8+ T cells, expressing either a high level (CD8Bright+) or a low level (CD8Dim+) of CD8 molecules. The staining patterns of mAb AV14 and mAb CT8 were not always identical for individual chickens. In this study the discrepancy in the reactivity of these mAb was examined, using outbred White Leghorn chickens as well as (B14B14)-MHC inbred Wellcome chickens. The results show that mAb AV14 and mAb CT8 recognise different epitopes on the chicken CD8 alpha molecule. The CD8Bright+ cells appeared to express the CD8 alpha beta heterodimer and the CD8Dim+ cells the CD8 alpha alpha homodimer. Conformational differences between the alpha beta heterodimer and the alpha alpha homodimer could account for the differences in binding characteristics found for the two mAb. The existence of a polymorphism of the CD8 alpha molecule in outbred White Leghorn chickens was suggested by the failure of peripheral blood leucocytes from some chickens to react with mAb AV14. This heterogeneity was not observed in the Wellcome line.

Primary Sjögren's syndrome and psoriasis vulgaris in a case of OKT4 epitope deficiency

We report a 29-year-old female OKT4 epitope deficiency patient with primary Sjögren's syndrome and psoriasis vulgaris. Immunological investigations during the prolonged clinical course of her herpes zoster revealed that she has OKT4 epitope deficiency and primary Sjögren's syndrome. She had been treated for psoriasis vulgaris for 17 years without systemic immunosuppressive therapy. Flow cytometric study revealed that her OKT4 deficiency is heterogeneous and excluded interference with the OKT4 epitope by anti OKT4 autoantibodies. The rare coexistence of primary Sjögren's syndrome and psoriasis implicates an immune disturbance due to an unusual phenotype of CD4.

Flow cytometry analysis of OKT4 epitope deficiency in South African black children

A case of OKT4 epitope deficiency referred for investigation with suspected immunodeficiency is described. Flow cytometry analysis of OKT4 epitope deficiency in a study group of healthy black children showed different manifestations of the lack of OKT4 epitope; a complete lack of OKT4+CD4+ peripheral blood lymphocytes (PBL) with normal numbers of OKT4A+ and Leu3a-CD4+ PBL, decreased percentage OKT4+CD4+ compared with OKT4A+ and Leu-3a+CD4+ PBL, decreased fluorescent staining intensity with OKT4 and a biphasic OKT4 staining pattern associated with a reduced OKT4/Leu-3a ratio. The percentage and fluorescent intensity of OKT4+CD4+ PBL in the study group were significantly lower (P < 0.0001) than Leu-3a+CD4+ and OKT4A+CD4+ PBL. There is thus considerable risk of under-estimating the number of CD4+ cells in black South Africans if the OKT4 MoAb is used.

A single amino acid substitution in a common African allele of the CD4 molecule ablates binding of the monoclonal antibody, OKT4

The CD4 molecule is a relatively non-polymorphic 55 kDa glycoprotein expressed on a subset of T lymphocytes. A common African allele of CD4 has been identified by non-reactivity with the monoclonal antibody, OKT4. The genetic basis for the OKT4- polymorphism of CD4 is unknown. In the present paper, the structure of the CD4 molecule from an homozygous CD4OKT4- individual was characterized at the molecular level. The size of the CD4OKT4- protein and mRNA were indistinguishable from those of the OKT4+ allele. The polymerase chain reaction (PCR) was used to map the structure of CD4OKT4- cDNAs by amplifying overlapping DNA segments and to obtain partial nucleotide sequence after asymmetric amplification. PCR was then used to clone CD4OKT4- cDNAs spanning the coding region of the entire, mature CD4 protein by amplification of two overlapping segments followed by PCR recombination. The nucleotide sequence of CD4OKT4- cDNA clones revealed a G----A transition at bp 867 encoding an arginine----tryptophan substitution at amino acid 240 relative to CD4OKT4+. Expression of a CD4OKT4- cDNA containing only this transition, confirmed that the arginine----tryptophan substitution at amino acid 240 ablates the binding of the mAb OKT4. A positively charged amino acid residue at this position is found in chimpanzee, rhesus macaque, mouse and rat CD4 suggesting that this mutation may confer unique functional properties to the CD4OKT4- protein.

Guidelines for the care of children and adolescents with HIV infection. Immunologic considerations in pediatric HIV infection

The pervasive effect of HIV infection on the immune system requires that the clinician be alert to the variety of immunologic abnormalities that can result from this disease. The tests described in this section provide guidelines for testing the HIV-infected child. Additional information on immunologic evaluations in the child with indeterminate HIV infection status can be found in the article on ambulatory care.

Humans with OKT4-epitope deficiency have a single nucleotide base change in the CD4 gene, resulting in substitution of TRP240 for ARG240

The OKT4 epitope of the CD4 cell-surface protein has been shown to be polymorphic in white, black, and Japanese populations. The variable phenotypic expression is due to an alteration of the OKT4 epitope, since those persons lacking reactivity with OKT4 monoclonal antibody (mAb) are reactive with OKT4A-F mAb as well as other mAb specific for CD4. To determine the nature of this polymorphism at the gene level, we sequenced polymerase chain reaction-amplified genomic DNA containing the CD4-V3 and -V4 exons from American black subjects who are OKT4-normal, OKT4-negative heterozygous, or OKT4-negative homozygous. Comparison of the sequences revealed that the two CD4 exons are identical except for a cytosine-to-thymidine transition occurring at nucleotide position 868. This alters the first codon position of mino acid 240 and results in a tryptophan residue replacing an arginine residue. The change was also found in white and Japanese persons who are OKT4-negative.

Maturation or differentiation of human thymocyte precursors in vitro?

The differentiation or maturation potential of human thymocyte precursors has been studied by using a population of CD3/TCR-, CD4-, CD8- ("triple negative") thymocytes isolated by negative selection (TCR, T-cell receptor). This cell population, however, also contained 30-50% previously undescribed cells expressing very low levels of CD3/TCR gamma delta (CD3/TCR gamma delta low; approximately 60% of which expressed the variable region gene V delta 1). Correspondingly, TCR gamma and TCR delta gene rearrangements (predominantly V delta 1/joining region J delta 1) and full-length TCR gamma and TCR delta transcripts (but only immature TCR beta and no TCR alpha mRNAs) were found. These cells mobilized Ca2+ in response to ligation of CD3 but not following ligation of TCR gamma delta. When cultured in the presence of interleukin 7 or interleukin 2, these thymocytes gave rise to 30-60% CD3/TCR gamma delta medium and high cells (60-70% expressing V delta 1) seen as discrete populations. Thus, the proportion and V delta phenotype of in vitro generated CD3/TCR gamma delta cells closely resembled those of CD3/TCR gamma delta low cells in freshly isolated "thymocyte precursor" preparations. Small numbers of TCR alpha beta + cells also appeared. It is thus uncertain whether maturation, differentiation, or both account for the appearance of mature CD3/TCR+ thymocytes, although the former appears most likely.

Topographic map of the HLA-A2 CREG epitopes using human alloantibody probes

The topographic architecture of the epitopes expressed on the HLA-A2 glycoprotein using murine monoclonal antibody (mAb) probes indicates at least two sterically distinct domains. Previously, we have demonstrated using human HLA alloantibodies (aAb) that multiple determinants are expressed on each HLA antigen: the highly polymorphic private epitopes and the public determinants that are shared within a family of crossreactive groups (CREG). Our objectives now focus on probing the antigenic structure of the HLA-A2-28-9-B17 CREG using highly specific aAb in conjunction with mAb that have previously been used for structural studies. Both mAb-mediated blockage of complement-dependent cytotoxic aAb and reciprocal antibody (Ab) binding inhibition assays with quantitation by fluorescence flow cytometry have been utilized. We have found that xenogeneic mAb directed against A2-69, A2-B17, and A2-28 crossblock aAb of the same serologic specificity, and vice versa, indicating that the epitopes they respectively recognize are at least in close steric proximity. However, additional HLA-A2, A28, and B17 aAb of private specificity and A2-28-9 aAb of public specificity, for which there are no known mAb counterparts, paint an additional complexity not previously known. We conclude that at least four different alloepitopes can be expressed by each serologically defined HLA antigen. Based on the primary sequence data, we have assigned the location and the amino acid substitutions which most likely account for these discrete epitopes. The unique private determinants are located on the alpha 1 domain together with the interlocus A2-B17 epitope while the public epitopes A2-69, A2-28-9 and A2-28 are located on the alpha 2 domain.

T-cell subsets in healthy teenagers: transition to the adult phenotype

Little is known about the normal range and variability of T-cell subsets in older children. We analyzed peripheral blood mononuclear cell subsets in 112 healthy children, ages 12-19 years (mean +/- SD: 15.4 +/- 1.9 years), using monoclonal antibodies and flow cytometry. The study population included 28 blacks and 84 whites, with 59 boys and 53 girls. The mean +/- SD cell subset values were: CD3+ T cells, 74.0 +/- 7.8%; CD4+ helper-inducer T cells, 46.8 +/- 6.9%; CD8+ suppressor-cytotoxic T cells, 27.3 +/- 5.7%; CD4:CD8 helper:suppressor ratio, 1.81 +/- 0.57; CD16+ natural killer cells, 4.4 +/- 3.1%; CD19+ B cells, 10.0 +/- 5.3%; CD14+ monocytes, 20.0 +/- 6.5%; and HLA-DR cells, 15.4 +/- 4.8%. Overall, boys had a higher proportion of HLA-DR+ cells than girls, attributable to an increase in CD19+ B cells. Blacks tended to have a higher proportion of HLA-DR+ cells than whites, apparently due to an increase in activated T cells. Detailed analysis by age group revealed a striking transition in the pattern of CD4+ and CD8+ cell populations. The CD4:CD8 ratio, higher in boys than girls for ages 12-16, was reversed to the "adult" pattern in 17-19 year olds, with a higher CD4:CD8 ratio in girls. These data provide important baseline values for healthy children and stress the importance of establishing normative ranges for pediatric subjects separately from adults.

Effects of sensitization to dinitrochlorobenzene (DNCB) on clinical pathology parameters and mitogen-mediated blastogenesis in cynomolgus monkeys (Macaca fascicularis)

Immunotoxicologic testing of drug candidates and environmental contaminants is of growing importance. Cutaneous delayed type hypersensitivity (DTH) is a convenient way of testing immune function in vivo. However, DTH testing must not interfere with interpretation of other relevant parameters. We have evaluated the effects of sensitization and challenge with dinitrochlorobenzene (DNCB) on clinical parameters routinely evaluated in toxicity testing and on lectin-mediated blastogenesis. Female cynomolgus monkeys were sensitized to DNCB with 4 daily applications of DNCB in acetone to the skin of the axilla. Fifteen days later, the monkeys were challenged for DTH by applying DNCB to the antecubital skin. Skin fold thickness was measured and the macroscopic appearance of the challenge site was scored 24 and 48 hr after challenge. All 5 monkeys were successfully sensitized to DNCB. There was a significant increase in the mean skin fold thickness (compared to pre-challenge thickness) of 2 mm at 24 hr and 1 mm at 48 hr (p less than 0.001). The clinical score of the challenge site was also increased. Histologic examination of the sensitization and challenge sites from a second group of monkeys exposed to DNCB in an identical manner showed the perivascular inflammatory cell infiltrate typical of DTH. Evaluation of hematologic parameters at days 7, 14, and 21 revealed no change in the erythron at any interval and a mild decrease in total WBC, neutrophil and lymphocyte counts on day 7 in 4/5 monkeys. The WBC parameters remained within the normal range and returned to pre-sensitization values at the later intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined immunodeficiency due to the selective absence of CD4 inducer T lymphocytes

Selective congenital deficiency of the CD4 inducer T lymphocyte subset is a recently described variant of combined immunodeficiency. To further characterize the cellular and molecular mechanisms which lead to the profound T and B cell immunodeficiency in this condition, we examined in vitro immunoregulatory T lymphocyte activation and effector function, interleukin-2 (IL-2) synthesis, IL-2 receptor generation, and CD4 gene structure. Immunophenotyping of T lymphocytes demonstrated a selective deficiency of CD4+ cells, with normal numbers of CD2+ and CD3+ T cells, nearly all of which expressed the CD8+ determinant. Mitogen- and alloantigen-induced blastogenesis was profoundly decreased. B lymphocytes were present in normal numbers but there was a functional dysgammaglobulinemia (low IgG, normal IgM, low IgA) with no antibody response to in vivo immunization. T cells from the patient did not provide help to normal B cells for in vitro immunoglobulin synthesis; however, the patient's B cells were capable of synthesizing normal amounts of IgG when provided help from normal T cells. Concanavalin A failed to activate suppressor-inducer function in the patient's T cells. However, CD8+ T cell-mediated suppression was expressed if the patients T cells were cocultured with normal CD4+ T cells in a pokeweed mitogen-stimulated IgG secretion assay. IL-2 secretion and IL-2 receptor expression were both markedly reduced. Southern blot analysis of genomic DNA revealed no obvious abnormality in CD4 gene structure. The global defects in T cell activation, effector function, immunoregulation, and lymphokine generation observed in CD4+ inducer lymphocyte deficiency emphasizes the central role that the CD4 T lymphocyte plays in the activation and regulation in vivo immune responses.

In vitro binding and internalization of HIV envelope glycoproteins by human epidermal Langerhans cells does not require the CD4-gp120-binding site

Langerhans cells (LC) are epidermal dendritic cells which express several surface antigens, among them the CD4 antigens. Recent data demonstrated that LC constitute target and storage cells for HIV. To better understand the interactions between HIV and LC, we investigated, in the present work, the fate of HIV envelope glycoproteins (gp120 and gp160) incubated with healthy human trypsinized LC in suspensions. After trypsin treatment, only the epitope for OKT4 appeared to be resistant on LC. In the absence of antigenic sites identified by OKT4A, Leu3a or BL4 (epitopes implicated in HIV binding), LC bound and internalized recombinant HIV gp120 or gp160. This finding supports the hypothesis that there exists at the surface of LC a second molecule which may act as an HIV receptor.

Lack of Leu-3a epitope on T-helper (CD4) lymphocytes

Human T-helper cells express membrane-bound CD4 antigen whose many epitopes are recognized by different monoclonal antibodies. The epitope recognized by Leu-3a and similar clones has been shown to be the location for human immunodeficiency virus (HIV) receptor. We have found a unique blood donor whose CD4+ T-helper lymphocytes were lacking Leu-3a epitope. CD4+ T-helper cells lacking Leu-3a epitope might be resistant to HIV infection.

Role of CD4 in normal immunity and HIV infection

In this report we have attempted to review our knowledge of the role(s) of CD4 in human T-cell function and the consequences of interactions between CD4 molecules and the human immunodeficiency virus (HIV). The observation in 1981 that antibodies to certain epitopes of CD4 inhibited the immune functions of CD4+ T cells led to the initial suggestion that CD4 molecules play a direct role in T-cell function. Although the precise functions of CD4 remain incompletely understood, a preponderance of evidence suggests that this molecule may in fact serve several critical roles. At least one such role is that of interacting directly with MHC class II molecules on antigen-presenting cells, presumably facilitating cell-to-cell interactions. On activated CD4+ T cells, CD4 molecules can also interact directly with the T-cell receptor complex to influence the immune response. Unfortunately, in addition to interacting with the T-cell receptor and class II MHC determinants, CD4 serves as a high affinity receptor for HIV, the causative agent of AIDS. Not only does interaction between the virus and CD4 initiate viral fusion to the cell membrane and HIV entry but, in addition, a similar molecular interaction initiates fusion between HIV-infected and uninfected CD4+ cells, resulting in the formation of multinucleated syncytia. Since uninfected CD4+ cells are, in effect, recruited into such syncytia, this mechanism may account in part for the depletion of CD4+ T cells in HIV-infected patients. Soluble forms of CD4 produced either by genetic engineering or solid phase peptide synthesis can completely block HIV infectivity and syncytia formation in vitro, remarkably without apparent effects on T-cell immunity. Such molecules are currently being explored for their possible therapeutic effects on HIV infection in vivo.

The influence of age, race, and gender on peripheral blood mononuclear-cell subsets in healthy nonsmokers

To investigate the influence of age, race, and gender on the cellular immune system, we determined T-cell, B-cell, monocyte, natural killer (NK)-cell, and HLA-DR+-cell subsets in 266 nonsmokers from a population-based random sample of healthy adults using monoclonal antibodies and flow cytometry. Blacks had a lower total white blood-cell count than whites (P less than or equal to 0.0001), due primarily to a decrease in granulocytes. There was no significant difference in absolute lymphocyte count between blacks and whites. Blacks had a higher proportion of CD19+ cells (Leu 12+ B cells) and a lower proportion of CD3+ cells (OKT3+ T cells) than whites (P less than or equal to 0.01). Female sex and increasing age were independently associated with an increased percentage of CD4+ cells (OKT4A+ helper-inducer T-cell subset), resulting in a higher helper/suppressor ratio among women and older individuals (P less than or equal to 0.05). Black race and increasing age were independently associated with an increased proportion of HLA-DR+ cells (P less than or equal to 0.0001) which was not attributable to B cells or monocytes. No significant age, race, or gender effects were observed for CD14+ cells (Leu M3+ monocytes) or CD16+ cells (Leu 11A+ natural killer cells). These data demonstrate that age, race, and gender are each associated with significant differences in peripheral blood mononuclear-cell subsets. Population-based data such as these provide an important foundation for future design and interpretation of human flow cytometry data.

Binding region for human immunodeficiency virus (HIV) and epitopes for HIV-blocking monoclonal antibodies of the CD4 molecule defined by site-directed mutagenesis

The binding region for human immunodeficiency virus (HIV) and epitopes for a panel of HIV-blocking anti-CD4 monoclonal antibodies of the CD4 molecule were defined by using in vitro site-directed mutagenesis. Codons for two amino acid residues (Ser-Arg) were inserted at selected positions within the region encoding the first and second immunoglobulin-like domains of CD4. A vaccinia virus-based expression system was used to produce soluble full-length extracellular CD4 fragments containing the insertions. The mutant proteins were tested for direct binding to soluble gp120 (the CD4-binding subunit of the viral envelope glycoprotein) and to a series of HIV-blocking anti-CD4 monoclonal antibodies. Impaired gp120 binding activity resulted from insertions after amino acid residues 31, 44, 48, 52, 55, and 57 in the first immunoglobulin-like domain. The epitopes for two HIV-blocking monoclonal antibodies, OKT4A and OKT4D, were also mapped in the gp120-binding region in the first domain. Insertions after amino acid residues 21 and 91 in the first domain had no effect on gp120 binding but impaired the binding of OKT4E, suggesting that this antibody recognizes a discontinuous epitope not directly involved in gp120 binding. Moderate impairment of gp120 binding resulted from the insertion after amino acid residues 164 in the second immunoglobulin-like domain, where the epitopes for monoclonal antibodies MT151 and OKT4B were also mapped.

Expression of human CD4 by two human-mouse interlineage hybrids

Two hybrid cell lines expressing human CD4 were prepared by fusing human B-lymphoid cells with the mouse T-lymphoma BW5147. Hybrid TF42 was derived from a human B-lymphoblastoid line and TF53.1 from a human B-ALL. Variants of these hybrids expressing or lacking CD4 were isolated by sorting cells stained with the monoclonal antibody (mAb) OKT4 on a fluorescence-activated cell sorter (FACS). Cytogenetic, isoenzyme and DNA analysis confirmed the presence of human chromosome 12 in the CD4+ hybrids, and revealed that CD4 expression by TF42 was associated with multiple copies of this chromosome. Of seventy mAb recognizing human T-cell antigens screened on the CD4+ and CD4- variants of the two hybrids, only mAb recognizing CD4 and Leu 8 reacted with the CD4+ cells. These hybrids should be useful in the preparation, screening and analysis of anti-CD4 monoclonal antibodies, and in studies of CD4 epitopes recognized by HIV.

The immunological profile in sickle cell anaemia: a study of patients in the Arab Peninsula

Recurrent and often serious infections are common in sickle cell anaemia. The predisposing causes are multiple, and immune abnormalities are frequently blamed. In this study, immune complexes, lymphocyte subpopulations, immunoglobulins and complement were determined in 40 Arabs with sickle cell anaemia to ascertain some aspects of their immunological profile. Immunoglobulins were found to be either normal or high, C3 and C4 values mostly clustered at the lower level of normal with a few values below normal, and some patients had low T4/T8 lymphocyte ratios. The results are discussed and compared with previous studies.

Interleukin 1-induced down-regulation of antibody binding to CD4 molecules on human lymphocytes

Interleukin 1 (IL-1) is involved in the early activation of T lymphocytes. The CD4 antigen, described as a phenotypic marker of helper T cells, is also important in early T-cell activation by its ability to bind to MHC class II molecules on antigen-presenting cells, and to transmit positive (and negative) signals to the cells. We observed that purified human monocyte IL-1 as well as recombinant IL-1 alpha and IL-1 beta selectively decreased the binding of monoclonal antibodies to CD4 on the surface of otherwise unstimulated blood T cells, in contrast to prestimulated and continuously grown CD4+ cells. Under optimal growth conditions, the initial reduction in antibody binding to CD4 was followed by an apparent re-expression of the CD4 antigen even in the presence of high concentrations of IL-1. This re-expression did not occur if the cells were cultured at 4 degrees C, or after treatment with actinomycin D or cytochalasin B, indicating that protein synthesis and intact microfilament function were essential for re-expression of CD4 binding. The mechanism by which CD4 molecules are physically and/or functionally modulated by IL-1 is unclear.

A soluble recombinant polypeptide comprising the amino-terminal half of the extracellular region of the CD4 molecule contains an active binding site for human immunodeficiency virus

Infection of helper T lymphocytes by human immunodeficiency virus is initiated by a specific interaction of the viral envelope glycoprotein with CD4, an integral membrane glycoprotein of the target cell. We have adapted a vaccinia virus-based mammalian cell expression system to produce variants of the CD4 molecule for structure-function studies. In this report we demonstrate that a truncated 180-amino acid fragment representing approximately the N-terminal half of the extracellular region of CD4 is found primarily in soluble form in the extracellular medium. Epitope analysis with a panel of anti-CD4 murine monoclonal antibodies indicates that the fragment reacts with those antibodies known to block the interaction between CD4 and the human immunodeficiency virus envelope glycoprotein but reacts poorly or not at all with those antibodies that do not block this interaction. We also show that the fragment forms a specific complex with a soluble form of gp120, the CD4-binding subunit of the viral envelope glycoprotein. These results indicate that this soluble CD4 fragment contains an active binding site for human immunodeficiency virus.

Correlation between systemic lupus erythematosus and T4 epitope phenotype

Three groups of black subjects (systemic lupus erythematosus patients, patients with nonrheumatic disease, and normal subjects) were screened for the expression of the T4 epitope, as recognized by the monoclonal antibody OKT4. We found that the T cell subsets within each group were similar, regardless of the T4 epitope phenotype (intact, intermediate, or deficient). In the subgroup of Jamaican subjects, there was an association between systemic lupus erythematosus and the T4 epitope-intermediate and T4 epitope-deficient phenotypes; this association was not detected in the non-Jamaican population.

CD4+ T cell activation in multiple sclerosis

Interleukin-2 (IL-2) production by CD4-enriched T cells from multiple sclerosis (MS) patients and normal individuals stimulated with concanavalin A (conA) and/or autologous and allogeneic B lymphoid cell lines (B-LCL) was evaluated 24, 48 and 96 h after stimulation. ConA-stimulated CD4+ cells from MS patients did not produce significantly more IL-2 than normal CD4+ cells. In contrast, autologous B-LCL-induced IL-2 production by MS CD4+ cells significantly (P = 0.026) exceeded that produced by normal CD4+ cells identically stimulated after 24 h in culture. Differences in IL-2 production by CD4+ cells from MS patients reached highest significance using allogeneic B-LCL, whose stimulatory capacity was similar, whether established from normal individuals or MS patients. This increased IL-2 production in response to B-LCL may represent a supranormal response of CD4+ cells from MS patients to class II major histocompatibility (MHC)-associated stimuli. It suggests that the deficiency of suppressor T cell functions postulated to play a role in MS does not arise from a lack of IL-2 induction and might indicate that bursts of IL-2 production could play a role in MS.

Expression of differentiation antigens by hybrids of human lymphoblastoid cells

In previous communications, we have described the expression of class I and class II histocompatibility antigens by hybrids of human B and T lymphoblastoid cell lines (B- and T-LCL). In all cases, such hybrids were found to resemble their B-LCL parents, expressing high levels of class I and class II antigens encoded by both parent cell lines. In the current study, we have conducted a more extensive analysis of B-LCLxT-LCL hybrids with a panel of monoclonal antibodies recognizing a variety of B and T lymphocyte differentiation markers. Rather than exhibiting a B-LCL-dominant phenotype, most hybrids were found to express a majority of both T and B lymphocyte antigens expressed by their parent cell lines. Several hybrids of pairs of dissimilar T-LCL were also produced and analyzed. Again, a majority of parental antigens was expressed on the hybrids. However, eight of eight hybrids of the T-LCL CEM and HSB failed to express HNK-1, an antigen strongly expressed by HSB; and two hybrids of the T-LCL CEM and SKW3 expressed CD3, an antigen expressed by neither parent cell line.

New monoclonal antibodies that define multiple epitopes and a human-specific marker on the interleukin 2 receptor molecules of primates

Twelve hybridoma cell lines producing monoclonal antibodies to the human interleukin 2 (IL-2) receptor (IL-2R) molecule were prepared. These antibodies were characterized by competitive antibody-binding assay and sequential immunoprecipitation assay with four known monoclonal antibodies to the human IL-2R molecule. The twelve new monoclonal antibodies were divided among the four known antibody types, the HIEI-, H-A26-, H-31-, and anti-Tac-type, and an additional new type, the H-48-type. The H-48 antibody did not compete with any other antibodies in the competitive binding assay. The binding of 125I-IL-2 to MT-2 cells and the IL-2-dependent growth of normal activated T-cells were both strongly inhibited by all the H-31- and anti-Tac-type antibodies, and partially or slightly inhibited by HIEI- and H-A26-type antibodies, but were not inhibited by the H-48 antibody. Thus, the same type of monoclonal antibodies had a similar effect on the function of IL-2R. These results suggest that epitopes for the same type of antibodies could be single identical epitopes or epitopes closely associated with each other. On the other hand, these antibodies also reacted variously with a panel of various human and simian lymphoid cell lines immortalized with human T-cell leukemia virus type-I (HTLV-I): the H-45 antibody reacted only with the human cell lines, the H-C1 and H-44 and H-47 antibodies reacted with human and ape cell lines, and the other antibodies reacted with cell lines of humans, apes and Old and New World monkeys. These differences in the reactivity of the antibodies with the primate cell lines suggest that the antigenic structure of the IL-2R molecule changed during evolutionary divergence of the primates.

Serological and functional analysis of the epitope clusters on Leu3/T4 antigen

Monoclonal antibodies (MoAbs) were generated against cells or cell membrane glycoproteins of a human T-cell line, HPB-ALL. Five, designated MCN 1, 3, 12, 19, and 29, were found to be specific to helper/inducer T-cells; they gave a positive membrane staining to approximately 48% of peripheral blood lymphocytes and 84% of thymocytes and these proportions did not change upon costaining with Leu 3a, a known anti-helper/inducer T-cell MoAb. Furthermore, their reaction pattern with a panel of human lymphoid cell lines was identical to that of Leu 3a. A reciprocal binding blocking test showed that the epitopes reactive with the MCN MoAbs are divided into three separate clusters. The MCN 3- and Leu 3a-reactive epitopes formed a cluster and they appeared to be the same epitope. This cluster was well separated from that represented by the MCN 1-reactive epitope. The MCN 12-, 19-, and 29-reactive epitopes could be assigned to a third cluster. MCN 12 and 19 were probably toward the same epitope. A sequential binding test indicated that the three epitope clusters reside on the molecule carrying Leu 3a-defined epitope, i.e., the Leu3/T4 antigen. On the functional analysis, MCN 3 gave a profound inhibitory effect on T-cell proliferative response to MHC class II antigens, whereas other MCN MoAbs did not show any modifying effect on the T-cell function.

Binding of HTLV-III/LAV to T4+ T cells by a complex of the 110K viral protein and the T4 molecule

Human T-lymphotropic virus type III (HTLV-III) or lymphadenopathy-associated virus (LAV) is tropic for human T cells with the helper-inducer phenotype, as defined by reactivity with monoclonal antibodies specific for the T4 molecule. Treatment of T4+ T cells with monoclonal antibodies to T4 antigen blocks HTLV-III/LAV binding, syncytia formation, and infectivity. Thus, it has been inferred that the T4 molecule itself is a virus receptor. In the present studies, the surfaces of T4+ T cells were labeled radioactively, and then the cells were exposed to virus. After the cells were lysed, HTLV-III/LAV antibodies were found to precipitate a surface protein with a molecular weight of 58,000 (58K). By blocking and absorption experiments, this 58K protein was identified as the T4 molecule. No cell-surface structures other than the T4 molecule were involved in the antibody-antigen complex formation. Two monoclonal antibodies, each reactive with a separate epitope of the T4 molecule, were tested for their binding capacities in the presence of HTLV-III/LAV. When HTLV-III/LAV was bound to T4+ T cells, the virus blocked the binding of one of the monoclonal antibodies, T4A (OKT4A), but not of the other, T4 (OKT4). When HTLV-III/LAV was internally radiolabeled and bound to T4+ T cells which were then lysed, a viral glycoprotein of 110K (gp110) coprecipitated with the T4 molecule. The binding of gp110 to the T4 molecule may thus be a major factor in HTLV-III/LAV tropism and may prove useful in developing therapeutic or preventive measures for the acquired immune deficiency syndrome.

Monoclonal antibodies in studying immunological phenotypes of neoplastic diseases

Six hybridoma clones were obtained secreting monoclonal antibodies (Mab) against differentiating antigens of human hemopoietic cells. ICO-1 Mab detect Ia-like (Dr) antigens. Mab react with B-lymphocytes and monocytes without detecting antigens on granulocytes and T-cells. Antigen expression was enhanced following cell activation in a blast cell transformation test and mixed lymphocyte culture (MLC). ICO-1 Mab blocked MLC. The molecular weights of the antigen were 29 and 34 kilodaltons. Comparative studies of ICO-1 Mab with other Mab against Ia-like antigens revealed their identical reactivity. ICO-11 Mab detect the antigen on 4% of blood lymphocytes, 75% thymocytes, monoblasts, and CFU-GM. These Mab block NK-cell activity of blood mononuclear cells. ICO-GM-1 Mab detect the antigen on myelomonocytic cells and their precursors, but not CFU-GM. These Mab block binding of the C3Bi complement component to CR3 receptor and NK-cell activity. ICO-G2 Mab detect the antigen expressed at final stages of granulocyte differentiation. ICO-10 Mab detect the antigen on early thymocytes and ICO-02 on undifferentiated blast cells. Mab were shown to be applicable for human leukemia and lymphoma immune diagnosis.

Familial OKT4 epitope deficiency: studies on antigen density and lymphocyte function

The family of a case of hereditary deficiency of OKT4 epitope on helper T cells was investigated. A 30-year-old woman was found to have hardly any OKT4+ T cells (0.7%, normal 24-51%), but normal OKT3, OKT8, OKT11, OKIa1, Leu1, Leu2a, Leu3a, Leu7, and B1 positive cells. The response to mitogens (PHA, PWM, and Con A) and helper-or suppressor-T-cell functions of her peripheral lymphocytes were normal. She had normal helper-T-cell populations detected with OKT4A (39.1%) and Leu3a (39.5%) monoclonal antibodies. One of her sisters had the same defect, but other members of the family had normal lymphocyte subsets. Lymphocyte functions were also found to be normal in all family members examined. The peak position of the fluorescence intensity of OKT4+ cells was about half that of normal controls in five members of this family. Considering that these were carriers of OKT4 epitope deficiency, the OKT4 epitope abnormality was inherited as an autosomal codominant trait in this family. Similar OKT4 epitope deficiency with normal Leu3a+ and OKT4A+ cells was found in 38 of 8866 (0.43%) other subjects in Japan by the examination of routine blood samples.

Absence of the OKT4 epitope on blood T cells and thymus cells in a patient with thymoma, hypogammaglobulinemia, and red blood cell aplasia

Human helper/inducer T-lymphocytes that express the T4 antigen are important in the regulation of B and T cell functions. Several epitopes of the T4 molecule have now been recognized; however, the precise role of these molecules in the function of helper/inducer T cells is unclear. We studied a patient with thymoma, hypogammaglobulinemia, and red blood cell aplasia whose blood lymphocytes and thymus cells did not express the epitope recognized by OKT4 monoclonal antibody but did display the T4 epitopes recognized by OKT4A and Leu3A monoclonal antibodies. The absence of the OKT4 epitope on the patient's thymus cells suggested that the abnormality occurred during early T cell differentiation. The patient had intact delayed hypersensitivity to 4/4 antigens, and his blood lymphocytes proliferated normally to phytohemagglutinin, concanavalin A, pokeweed mitogen, tetanus toxoid, and allogeneic cells. The patient's T cells demonstrated augmented suppressor activity that was localized to the OKT8+ population rather than to the unusual T4 subset. Irradiation abrogated suppressor activity and rendered his T cells capable of providing help for polyclonal B cell differentiation. The data emphasize the limitations of OKT4 as the sole reagent for characterizing the subset of human helper/inducer cells and demonstrate that the expression of the T4 epitope recognized by OKT4 monoclonal antibody is not required for certain helper/inducer T cell functions in vitro and in vivo.

Systemic lupus erythematosus with deficiency of the T4 epitope on T helper/inducer cells

Three black Jamaicans with systemic lupus erythematosus (SLE) were identified whose T helper/inducer cells lacked the T4 epitope (T4 epitope-deficient phenotype). All three patients had lymphadenopathy as part of their syndromes. The asymptomatic and otherwise healthy T4 epitope-deficient brother of one of these patients also had lymphadenopathy in a distribution identical to that of his sister with SLE. Family studies pointed to an autosomal codominant mode of inheritance not linked to the HLA locus for the T4 epitope phenotype. Cultures of peripheral-blood mononuclear cells revealed impaired B-cell differentiation upon stimulation with pokeweed mitogen in cells originating from the T4 epitope-deficient family members as compared with those originating from their T4 epitope-intermediate relatives. Ratios of T helper/inducer cells to T suppressor/cytotoxic cells, the presence of various autoantibodies, and proliferation in response to mitogens and in the mixed lymphocyte reactions did not correlate with T4 epitope phenotype. We suggest that SLE in association with the T4 epitope-deficient phenotype may represent a unique subset of patients with SLE that has distinct clinical and immunologic properties.

Depression of lymphocyte responses to mitogens in mangabeys with disseminated experimental leprosy

Mononuclear cells from mangabey monkeys with disseminated experimental leprosy had increasingly severe depression of blastogenic responses to phytohemagglutinin, concanavalin A, and pokeweed mitogen as the disease progressed. Blastogenic responses were not depressed in cells from mangabeys with more localized disease. Blastogenic responses of cells from normal mangabeys appeared to vary with a circannual rhythm. The demonstration of significant negative correlations between the blastogenic responses to mitogens and the percentages of OKT8+ cells suggested that the mangabey OKT8+ subset may contain cells with suppressor function. The depressed responses to mitogens by cells from monkeys with disseminated experimental leprosy were associated with relatively high percentages of OKT8+ cells. Polyclonal immunoglobulin plaque-forming cell responses to pokeweed mitogen were depressed in cells from experimentally infected mangabeys. The results indicated that defects in immune regulation may occur in experimental leprosy in mangabeys, similar in some respects to the defects that have been reported in human leprosy.