Immunological studies in acquired immunodeficiency syndrome. Functional studies of lymphocyte subpopulations

Jak3, STAT3, and STAT5 inhibit expression of miR-22, a novel tumor suppressor microRNA, in cutaneous T-Cell lymphoma

Aberrant activation of Janus kinase-3 (Jak3) and its key down-stream effectors, Signal Transducer and Activator of Transcription-3 (STAT3) and STAT5, is a key feature of malignant transformation in cutaneous T-cell lymphoma (CTCL). However, it remains only partially understood how Jak3/STAT activation promotes lymphomagenesis. Recently, non-coding microRNAs (miRNAs) have been implicated in the pathogenesis of this malignancy. Here, we show that (i) malignant T cells display a decreased expression of a tumor suppressor miRNA, miR-22, when compared to non-malignant T cells, (ii) STAT5 binds the promoter of the miR-22 host gene, and (iii) inhibition of Jak3, STAT3, and STAT5 triggers increased expression of pri-miR-22 and miR-22. Curcumin, a nutrient with anti-Jak3 activity and histone deacetylase inhibitors (HDACi) also trigger increased expression of pri-miR-22 and miR-22. Transfection of malignant T cells with recombinant miR-22 inhibits the expression of validated miR-22 targets including NCoA1, a transcriptional co-activator in others cancers, as well as HDAC6, MAX, MYCBP, PTEN, and CDK2, which have all been implicated in CTCL pathogenesis. In conclusion, we provide the first evidence that de-regulated Jak3/STAT3/STAT5 signalling in CTCL cells represses the expression of the gene encoding miR-22, a novel tumor suppressor miRNA.

Wasik M, B. Koralov S, Geisler C, Kilian M, Iversen L, Woetmann A, Odum N. Bacterial toxins fuel disease progression in cutaneous T-cell lymphoma

In patients with cutaneous T-cell lymphoma (CTCL) bacterial infections constitute a major clinical problem caused by compromised skin barrier and a progressive immunodeficiency. Indeed, the majority of patients with advanced disease die from infections with bacteria, e.g., Staphylococcus aureus. Bacterial toxins such as staphylococcal enterotoxins (SE) have long been suspected to be involved in the pathogenesis in CTCL. Here, we review links between bacterial infections and CTCL with focus on earlier studies addressing a direct role of SE on malignant T cells and recent data indicating novel indirect mechanisms involving SE- and cytokine-driven cross-talk between malignant- and non-malignant T cells.

Vascular endothelial growth factor receptor-3 expression in mycosis fungoides

Here, we have studied vascular endothelial growth factor receptor-3 (VEGFR-3) expression in mycosis fungoides (MF), the most common type of cutaneous T-cell lymphoma (CTCL). Immunohistochemistry revealed that in two-thirds of 34 patients, VEGFR-3 was expressed in situ by both tumor and stromal cells irrespective of the disease stage. The natural VEGFR-3 ligand, VEGF-C, partially protected malignant T-cell lines from growth inhibition by the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA). Whereas the malignant T cells did not produce VEGF-C in vitro, its expression was induced during tumor formation in vivo in a xenograft mouse model of MF. In conclusion, malignant and stromal cells express high levels of VEGFR-3 in all stages of MF. Moreover, malignant T cells trigger enhanced VEGF-C expression in fibroblasts, suggesting that cross-talk between tumor and stromal cells plays a role in lymphangiogenesis and possibly disease progression.

IFN-α primes T- and NK-cells for IL-15-mediated signaling and cytotoxicity

Recently it has become clear that interferon (IFN)-α, a type I interferon produced rapidly in response to infection, not only plays a key role in innate immunity, but also promotes adaptive immune responses by influencing the production or function of other cytokines. During infections IFN-α fosters the production of IL-15, which plays a pivotal role in the development, survival and function of NK cells and recruitment and activation of T cells. Since these two cytokines exert overlapping functions during infections, this investigation was undertaken to study the priming effect of IFN-α on the effect of IL-15 on human T and NK cells. We show that IFN-α induces an increased expression of IL-15Rα in human activated peripheral T cells, and in CD8(+) and CD4(+) T-cell lines. Functionally, the IFN-α-enhanced IL-15Rα expression resulted in an enhanced IL-15-mediated phosphorylation of STAT5 and STAT3 followed by a further increase in IL-15Rα expression. Moreover, IFN-α significantly increased the IL-15-induced cytotoxic activity of freshly isolated T and NK cells. Taken together, our data show that IFN-α boosts signaling and functional effects of IL-15, at least in part by fostering the increased IL-15R expression, thus add new facet to the emerging role of IFN-α as an important primer of adaptive immune responses.

Programmed cell death-10 enhances proliferation and protects malignant T cells from apoptosis

The programmed cell death-10 (PDCD10; also known as cerebral cavernous malformation-3 or CCM3) gene encodes an evolutionarily conserved protein associated with cell apoptosis. Mutations in PDCD10 result in cerebral cavernous malformations, an important cause of cerebral hemorrhage. PDCD10 is associated with serine/threonine kinases and phosphatases and modulates the extracellular signal-regulated kinase pathway suggesting a role in the regulation of cellular growth. Here we provide evidence of a constitutive expression of PDCD10 in malignant T cells and cell lines from peripheral blood of cutaneous T-cell lymphoma (Sezary syndrome) patients. PDCD10 is associated with protein phosphatase-2A, a regulator of mitogenesis and apoptosis in malignant T cells. Inhibition of oncogenic signal pathways [Jak3, Notch1, and nuclear factor-κB (NF-κB)] partly inhibits the constitutive PDCD10 expression, whereas an activator of Jak3 and NF-κB, interleukin-2 (IL-2), enhances PDCD10 expression. Functional data show that PDCD10 depletion by small interfering RNA induces apoptosis and decreases proliferation of the sensitive cells. To our knowledge, these data provide the first functional link between PDCD10 and cancer.

Proliferative responses of blood mononuclear cells (BMNC) in a cohort of elderly humans: role of lymphocyte phenotype and cytokine production

Age-related impaired T cell function is associated with increased mortality risk. The purpose of the present study was therefore to identify factors associated with the age-related decreased phytohaemagglutinin (PHA)-induced proliferative response of lymphocytes in a cohort of 174 81-year-old humans and in 91 young controls. Decreased proliferation was associated with a reduced number of true naive CD4+ cells (CD62L+CD45RO-). Furthermore, a low IL-2-stimulated proliferation was correlated with a decreased PHA response in the elderly cohort, whereas reciprocal interactions of IL-10- and IL-2-producing cells were of importance in both elderly and young subjects. Accordingly, a minimum of true naive CD4+ cells was required for a normal proliferative response to PHA, perhaps by providing sufficient IL-2 which is critical for growth of naive as well as memory cells.

Defective T-cell stimulatory pathways in patients after allogeneic bone marrow transplantation (BMT) in man

Immunological reconstitution after allogeneic bone marrow transplantation in man is characterized by a decreased lymphocyte transformation response to various mitogens and antigens during a period of from months to years. One reason for the decreased proliferative capability could be an inverted CD4/CD8 ratio; however, the present investigation demonstrates that this is not the only explanation for the immunodeficiency, since the CD4 as well as the CD8 subset, when studied in isolation, have qualitative defects, as evidenced by a reduced response of both subsets to stimulation with PHA, anti-CD2 and anti-CD3 MABs. The reason for the qualitative defect is unknown but a distorted composition of the CD4+ as well as the CD8+ T-cell subsets is suggested by the present investigations. We also observed that the PHA response was almost completely reconstituted one year after BMT, while the PWM response was still severely affected. The present study suggests that T-cell subsets which differ in their capacity to respond to PHA and PWM have different kinetics of reconstitution after BMT.

Serum increases and lymphoid cell surface losses of IL-2 receptor CD25 in HIV infection: distinctive parameters of HIV-induced change

Lymphocyte activation induces production of soluble IL-2 receptor (sIL-2R) which is a large portion of the CD25 membrane molecule and which is detectable in serum. Serum sIL-2R is reported here to increase as a direct effect of the HIV infection and not to be due to secondary opportunistic infections. sIL-2R increased promptly after HIV seroconversion in 83% of 50 initially seronegative homosexual men. The sIL-2R serum levels stabilized in the third year after seroconversion and were then predictive of later CD4 T cell levels and development of AIDS. In two studies of 59 and 395 seropositive men, beta-2 microglobulin (B2M) and neopterin levels in serum correlated closely with each other but not with sIL-2R levels. Thus, increased production of sIL-2R may reflect pathological processes distinct from those determining B2M and neopterin increases. Membrane CD25 expression on peripheral blood lymphocytes, unexpectedly, was found to be decreased in HIV infection. This contrasted with the increased sIL-2R in serum. Investigations with sensitive flow cytometry technics showed that CD25 was expressed at reduced levels and averaged only 12% of lymphocytes from HIV-infected individuals in contrast to 25% in noninfected individuals. All major lymphoid populations showed reductions in CD25 positive cells. This reduction in lymphoid membrane CD25, however, was not inversely correlated with the increased serum levels of sIL-2R or with other parameters of immune deficiency or activation. Thus, surface CD25 loss and serum sIL-2R increase are separate and independent consequences of HIV infection.

Immunological marker analysis of mitogen-induced proliferating lymphocytes using BrdU incorporation or screening of metaphases. Staphylococcal protein A is a potent mitogen for CD4+ lymphocytes

The proliferative effects of the mitogens phytohaemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM), and staphylococcal protein A (SpA) were investigated using two different methods which enable immunological marker analysis of proliferating cells: either surface marker labelling followed by BrdU incorporation or screening of metaphases after surface marker labelling. Therefore peripheral blood mononuclear cells from six healthy volunteers were stimulated with these four mitogens. Both PHA and Con A gave rise to more CD8+ than CD4+ proliferating cells. PHA, but not Con A, induced B-cell proliferation as well. PWM mainly caused T-cell proliferation. SpA also appeared to be a potent T-cell mitogen in addition to its capacity to induce B-cell proliferation. However, in contrast to the other mitogens SpA predominantly stimulated CD4+ cells.

Investigation of immunosuppressive properties of inactivated human immunodeficiency virus and possible neutralization of this effect by some patient sera

Retroviral infections are accompanied by immunosuppression in a variety of species. For feline leukemia virus, the immunosuppression has been ascribed to the transmembrane envelope protein, p15E, which suppresses the proliferative responses of cat, mouse, and human lymphocytes. A similar suppressive effect has been shown for a lysate of human immunodeficiency virus (HIV), strain HTLV-IIIB. Here we determined that detergent-disrupted HTLV-IIIB lystate exerted a strong suppressive effect on PHA-stimulated lymphocytes. Preparations of whole virions, a lysate of a local HIV isolate grown on MP-6 cells, and a commercially obtained UV and psoralene-inactivated lysate were examined and demonstrated to have a similar suppressive effect. The HIV lysate was not directly cytotoxic to lymphocytes and did not contain tumor necrosis factor or lymphotoxin. The HIV lysate specifically suppressed the proliferation of a range of hemopoietic cell lines from man and mouse including three EBV transformed CD4- and IL-2 receptor-negative B-cell lines. The lysate also suppressed the formation of human bone marrow colonies, whereas the lysate had only a slight or no effect on fibroblasts. The suppression of lymphocyte proliferation was not abrogated by addition of IL-2 or IL-1 and the HIV lysate inhibited the expression of IL-2 receptors on suboptimal PHA-stimulated mononuclear cells. The suppressive factor(s) has not been characterized in molecular terms, but suppressive activity was recovered in fractions with a molecular weight of about 67,000 and in both the glycoprotein fraction and in the glycoprotein-depleted fraction of the HIV lysate. Sera from one-third of a small series (N = 13) of individuals with antibodies to HIV seem to be able to neutralize the suppressive properties of HIV lysate in cultures.

Stimulation of AIDS lymphocytes with calcium ionophore (A23187) and phorbol ester (PMA): studies of cytoplasmic free Ca, IL-2 receptor expression, IL-2 production, and proliferation

We have studied whether the decreased lymphocyte proliferative responses of AIDS lymphocytes to stimulation by mitogens and antigens may be overcome when challenged with a combination of calcium ionophore A23187 and phorbol ester PMA. Comparison of the proliferative response of lymphocytes from nine patients with AIDS with the response of lymphocytes from nine control subjects showed that the response of AIDS lymphocytes was severely decreased when stimulated with PHA and no further response could be achieved by stimulation with A23187/PMA. On the other hand, no significant difference between the PHA-induced rise of cytoplasmic free calcium concentration ([Ca2+]1) in normal and AIDS lymphocytes was observed. The percentage of cells expressing IL-2 receptors (CD25) was also normal both after addition of PHA and after addition of A23187/PMA and the expression was normal on both CD4 and CD8 cells. The production of IL-2 in normal lymphocytes stimulated with A23187/PMA was 33 times higher than that after stimulation with PHA. In AIDS lymphocytes the production of IL-2 induced by all activators was severely decreased compared to control subjects, although the production of IL-2 after stimulation with A23187/PMA was higher than that in control lymphocytes after stimulation with PHA. The present study shows that a direct activation of protein kinase C combined with mobilization of cytoplasmic calcium does not overcome the lymphocyte proliferative deficiency of AIDS lymphocytes.

Prognostic value of immunologic abnormalities and HIV antigenemia in asymptomatic HIV-infected individuals: proposal of immunologic staging

The prognostic value of various immunologic tests was investigated in 150 HIV-seropositive homosexual men, who were initially without HIV-related symptoms or AIDS and who were followed for a median of 12 months (range 3-28 months). The laboratory investigations included HIV antigen in serum, total lymphocyte count, T-helper (CD4) and T-cytotoxic/suppressor (CD8) counts, and lymphocyte transformation responses to the mitogens phytohemagglutinin (PHA) and pokeweed mitogen (PWM), and to antigenic extracts from Candida albicans and cytomegalovirus. 24 individuals developed HIV-related symptoms or AIDS (11 cases). All parameters except the CD8 count were of prognostic value, but a multivariate analysis of symptom-free survival showed that HIV antigenemia, a CD4 count less than 0.5 x 10(9)/l, and relative response to PWM below 25% of controls contained all the prognostic information. Individuals abnormal at entry for these 3 variables had a theoretical 36 times as high hazard of developing symptoms within the observation period as had individuals with normal parameters. There was no significant covariation between HIV antigenemia on the one hand and CD4 count and response to PWM on the other. Although, the latter 2 variables covaried, each of them provided independent information, and both were used to classify the degree of the immunodeficiency in 3 stages: Im-0 with normal values, Im-1 with one, and Im-2 with both tests abnormal. Individuals in stage Im-2 had a 10 times increased risk of developing symptoms. The immunologic staging correlated significantly with the clinical grouping (CDC criteria). This staging improved in only 1, but deteriorated in half of 36 individuals observed for at least 18 months. Thus, the staging is likely to prove useful when attempts to arrest the immunodeficiency of HIV-infected individuals has to be monitored.

Effect of thapsigargin on cytoplasmic Ca2+ and proliferation of human lymphocytes in relation to AIDS

The tumor-promoting sesquiterpene lactone, thapsigargin, induced a dose-dependent increase of the cytoplasmic Ca2+ concentration ([ Ca2+]i) in human lymphocytes from a resting level between 100 and 150 nM up to about 1 microM. Half-maximum response was found at about 1 nM of thapsigargin, full response at 100 nM. The effect of thapsigargin on [Ca2+]i exceeded that of phytohaemagglutinin (PHA) which raised [Ca2+]i to maximum 300 nM. In combination with phorbol 12-myristate 13-acetate (PMA), thapsigargin stimulated the proliferation of normal lymphocytes to the same extent as did PHA, whereas the thapsigargin/PMA treatment could not restore the defective proliferation of AIDS lymphocytes in spite of the increased [Ca2+]i. Thapsigargin or PMA added separately had no stimulatory effects on cell proliferation. The thapsigargin/PMA treatment caused an increase in the interleukin-2 (IL-2) production of the lymphocytes, which was much higher than that caused by the PHA treatment, even in AIDS lymphocytes. Moreover, the thapsigargin/PMA treatment stimulated the expression of the IL-2 receptors on both normal and AIDS lymphocytes, similar to the effect of PHA. It is concluded that thapsigargin exerts its effects on lymphocyte proliferation by increasing [Ca2+]i, and that the general defect of AIDS lymphocytes, rather than being ascribed to the initiating signal systems, is associated with later events related to DNA synthesis and proliferation.

In vitro activation of T lymphocytes from HIV-seropositive blood donors. II. Decreased mitogen-induced expression of interleukin 2 receptor by both CD4 and CD8 cell subsets

Mononuclear cells (MC) from many individuals exposed to human immunodeficiency virus (HIV) exhibit a reduced proliferative response to a suboptimal concentration of phytohemagglutinin (PHA). However, the relative contributions of the 2 major T-cell subsets, namely CD4 and CD8 lymphocytes, to this reduced response remain unclear. Based on reports that interleukin 2 receptor (IL2R) expression correlates well with proliferative responses in HIV infection, we used dual-color cytofluorometry to measure IL2R expression by CD4 and CD8 cells following PHA activation of MC from HIV-seropositive blood donors. For data analysis, this study group was divided into two subgroups on the basis of DNA synthesis responses (seropositive with normal DNA synthesis, designated sero + NML, or seropositive with decreased DNA synthesis, designated sero + LOW). When compared to the seronegative control and sero + NML groups, the sero + LOW group exhibited significant reductions in the percentage of MC expressing IL2R, the proportion of CD4 cells expressing IL2R, and the proportion of CD8 cells expressing IL2R. In contrast, these parameters were unchanged in the sero + NML group compared to the control group. These findings show that reduced PHA-induced proliferative responses by MC from HIV-infected persons are associated with decreased IL2R expression by both CD4 and CD8 lymphocyte subsets.

Humoral and cellular responses to Pneumocystis carinii, CMV, and herpes simplex in patients with AIDS and in controls

The titers of IgG and IgA to Pneumocystis carinii in 36 AIDS patients did not differ significantly from those in 31 controls. Only 2/15 patients (13%) with P. carinii pneumonia (PCP) had titers of IgM antibodies greater than or equal to 5, which is significantly less frequent than in 32 controls (62%) and in 21 AIDS patients without PCP (43%). The risk of PCP was 5 times higher in patients without IgM antibodies to P. carinii than in patients who had these antibodies. A significantly higher percentage of those without PCP (57%) showed increasing titers of IgM antibodies to P. carinii in the second of paired samples taken about 6 months apart, compared with whose with PCP (9%; p = 0.05). All patients had high titers of antibodies to CMV and HSV and normal total concentrations of immunoglobulins. None of the patients responded in lymphocyte transformation to P. carinii, CMV, or HSV antigens. There is no obvious explanation to the selective lack of IgM antibodies to P. carinii in patients with PCP. Lack of IgM antibodies may be a marker for an immunodeficiency to P. carinii.

Function of pokeweed mitogen-stimulated human T cells following vaccination with pneumococcal polysaccharides

The T cell regulation of pneumococcal polysaccharide (PPS)-specific B cells was investigated in pokeweed-mitogen (PWM)-stimulated cultures. The numbers of anti-PPS-secreting cells (SC) increased in cultures of mononuclear cells (MNC) established two weeks after the vaccination, as compared to cultures established before vaccination (from 18/10(6) MNC to 45/10(6) MNC). This finding was most likely explained by an increase in the blood of B-cell precursors with specificity for PPS. B cells spontaneously secreting anti-PPS were found only in cultures established one week after vaccination. However, the presence of PWM and T cells increased the numbers of anti-PPS-SC also in these cultures, indicating that not all PPS-specific B cells are fully differentiated in vivo one week after vaccination. The vaccination-induced changes in T cell function were investigated by recombining cryopreserved T cells or T helper cells (CD8 negative cells) with freshly isolated autologous B cells from post-vaccination day 15. The numbers of total Ig-SC in cultures containing day 13 T cells were significantly lower than the numbers in cultures containing day 0 T cells (3958/10(6) MNC versus 5887/10(6) MNC). The same tendency was observed for anti-PPS-SC; this difference, however, was not significant. No differences were observed in the ability of T helper cells to support the generation of total Ig-SC and anti-PPS-SC. Irradiation (2300 rad) of T cells from day 0 increased the numbers of anti-PPS-SC in the cultures significantly (three times), whereas irradiation of day 15 T cells did not have a significant augmenting effect.(ABSTRACT TRUNCATED AT 250 WORDS)

The immunodeficiency of bone marrow-transplanted patients. II. CD8-related suppression by patient lymphocytes of the response of donor lymphocytes to mitogens, antigens, and allogeneic cells

Lymphocytes from 21 patients sampled 1-6 months after bone marrow transplantation (BMT) were tested for functional suppressor activity against marrow-donor lymphocytes in the lymphocyte transformation test. Suppression of donor responses to allogeneic (i.e. mixed lymphocyte reaction, MLR) and antigenic stimulation by irradiated (7600 rad) post-BMT cells was observed in about two-thirds of the combinations tested (N = 20 and N = 9). The suppression of donor MLR and antigen responses ranged between 5-52% and 10-46%, respectively. Irradiated post-BMT cells significantly suppressed donor responses to suboptimal concentrations of phytohaemagglutinin (PHA) (median suppression: 28%; P less than 0.05; N = 7) and concanavalin A (Con A) (median suppression: 31%; P less than 0.05; N = 6). A clearly suppressive effect of post-BMT cells was observed when the ratios of CD4+/CD8+ post-BMT cells were lower than 0.5 (P less than 0.01). In three experiments, the depletion of the CD8- but not of the CD4-positive subset abrogated the suppression of the donor MLR by post-BMT cells. The suppression by post-BMT cells (irradiated) of MLR and mitogen responses was comparable whether the responding cells were derived from the donor or from HLA-DR-incompatible, unrelated individuals. The proliferative capacity of post-BMT cells compared to that of donor cells was assayed in the MLR with unrelated, HLA-DR-incompatible stimulator cells. A significantly decreased proliferative capacity (median 20% of that of donor cells) was found (P less than 0.01; N = 16). A weak inverse correlation (P less than 0.05; N = 16) between the proliferative and the suppressive capacity of post-BMT cells in the MLR was observed. These findings indicate that the decreased proliferative capacity upon mitogen, antigen, and alloantigen stimulation observed in most patients within 1-6 months after BMT may be partly due to non-specific suppression by CD8+ cells.

Elevated plasma glutamate levels in colorectal carcinoma patients and in patients with acquired immunodeficiency syndrome (AIDS)

Amino acid concentrations were analyzed in the sera of HIV (LAV/HTLV-III) positive persons and in the plasma of colorectal carcinoma patients. Both groups of persons showed significantly elevated glutamate concentrations when compared with healthy control persons. Glutamate concentrations were found to be strongly elevated in all groups of HIV-positive persons including patients with acquired immunodeficiency syndrome (AIDS) or lymphadenopathy as well as HIV-positive persons without overt symptoms, indicating that increased plasma glutamate levels may be among the earliest consequences of the HIV infection. Moreover, the increased plasma glutamate concentrations in the colorectal carcinoma patients were correlated with a decreased immunological reactivity (mitogenic responses against concanavalin A). This suggests the possibility that the increased plasma glutamate concentrations may be causally responsible for the decreased immunological reactivity in colorectal carcinoma patients as well as in patients with AIDS.

Abnormality of Leu 2+7+ cells in acquired immune deficiency syndrome (AIDS), AIDS-related complex, and asymptomatic homosexuals

Peripheral blood mononuclear cells from patients with acquired immune deficiency syndrome (AIDS) and AIDS-related complex (ARC), asymptomatic homosexuals, and healthy heterosexuals were analyzed for the proportions and numbers of Leu 7+ cells and double-labeled Leu 2+7+ cells and for the natural killer functions. A significant increase in the proportions and numbers of Leu 7+ cells was observed in patients with AIDS and ARC and in asymptomatic homosexuals compared to healthy heterosexual men. The proportions of Leu 2+7+ cells were significantly increased in AIDS, ARC, and asymptomatic homosexuals, whereas the numbers were increased in asymptomatic homosexuals and ARC but not in AIDS compared to heterosexual controls. A significant increase in the number of Leu 2+7+ cells was observed in AIDS with Kaposi's sarcoma but not in AIDS with opportunistic infections. The natural killer function was significantly depressed in patients with AIDS and ARC and in asymptomatic homosexuals. These data suggest that the quantitative abnormalities of Leu 2+7+ cells appear early during the evolution of immunologic changes in HTLV III/LAV infection.

Proliferation induced by Plasmodium falciparum antigen and interleukin-2 production by lymphocytes isolated from malaria-immune individuals

Affinity-purified Plasmodium falciparum soluble antigens (SPAg) isolated from in vitro cultures of the parasite were shown to be relatively free of nonspecific polyclonal activators. To determine the presence of lymphocytes with specificity against SPAg in the peripheral blood of malaria-immune individuals, the proliferative response and the interleukin-2 (IL-2) production of SPAg-activated mononuclear cells (MNCs) from individuals unexposed, sensitized, and immune to malaria were measured. It was found that MNC isolated from malaria-immune individuals proliferated in response to SPAg and that this activation resulted in measurable IL-2 production in 5 of 10 MNC cultures. MNC isolates from most unexposed individuals did not respond to SPAg. To establish which cells responded to SPAg, different subpopulations of MNCs were tested. Only T helper cells were found to respond, and they responded only when cocultured with monocytes. The finding of parasite-specific T helper cells in the blood of malaria-immune individuals and the fact that some of these cells were able to produce IL-2 in vitro support the hypothesis that in malaria the cellular part of the protective immune response is initiated by immune T cells. These cells may activate nonspecific effector cells (i.e., macrophages) that eliminate the parasite.

Immunological studies in the acquired immunodeficiency syndrome. II. Active suppression or intrinsic defect--investigated by mixing AIDS cells with HLA-DR identical normal cells

The lymphocyte transformation responses to mitogens (phytohaemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM)), allogeneic cells, and the antigen-purified protein derivative (PPD) were studied in six acquired immunodeficiency syndrome (AIDS) patients and in six healthy controls, each of whom was HLA-DR- and mixed lymphocyte culture (MLC)-identical with one of the AIDS patients. No evidence of suppression was observed when irradiated or non-irradiated AIDS peripheral blood mononuclear cells (PBMC) were added to cultures of HLA-DR-identical PMBC from healthy controls stimulated with the strong mitogens PHA and Con A or with allogeneic cells, but suppression may be involved in the decreased responses in cultures stimulated with PWM or PPD. Addition of supernatants from macrocultures of AIDS cells did not suppress responses of control PBMC. Thus, suppression by any lymphocyte subset or soluble factor alone cannot explain the generally severely depressed transformation responses in AIDS. Addition of heavily irradiated HLA-DR-identical PBMC from healthy controls or supernatants from these cultures led to increased responses in cultures of mitogen-stimulated AIDS PBMC and in some cultures of antigen or allogeneic cell-stimulated AIDS PBMC, which were of the same magnitude as seen after the addition of commercially obtained T-cell growth factor (TCGF). This indicates that AIDS cells are deficient in producing TCGF. Heavily irradiated AIDS PBMC were capable of restoring the transformation responses to mitogens and antigens of purified HLA-DR-identical normal T cells, indicating that AIDS cells have a normal antigen-presenting capacity and interleukin (IL-1) production. However, AIDS PBMC had a very poor capacity to stimulate normal PBMC in MLC. Together, our experiments suggest that the immune deficiency in AIDS cells may be partially due to a decreased capability of T lymphocytes to produce TCGF and that a decreased number and/or function of dendritic cells may also be involved.

Cytotoxic capabilities of lymphocytes from patients with the acquired immunodeficiency syndrome

Lymphocytes from 16 AIDS patients were tested in the cell-mediated lympholysis assay (CML). The ability to produce alloreactive cytotoxic lymphocytes in vitro was found to be substantially reduced when compared with concomitantly investigated normal controls. Addition of interleukin 2 (IL-2) to the inducer cultures increased the cytotoxic activity, but not to normal levels. The CML response did not correlate with the relative or absolute number of Leu 3+ cells or the proliferation in effector suspensions. The ability to produce cytotoxic cells in CML, and the degree of potentiation by IL-2, was positively correlated with the absolute number of Leu 2+ cells in peripheral blood of the patients, which was below normal in 56% of the patients. It is suggested that the low CML in AIDS patients is primarily caused by defective T-cell help. In addition patients with decreased absolute numbers of Leu 2+ cells may have a reduced number of CTL precursors. The natural killer (NK) activity of AIDS lymphocytes was reduced, but could be improved by incubation with IL-2 in vitro. The mononuclear cells from the patients showed a decreased ability to respond and to stimulate in the mixed lymphocyte culture. In one of the AIDS patients, the CML was found to induce autoreactivity in vitro.

The immunodeficiency of bone marrow-transplanted patients. The effect of patient lymphocytes on the response of donor lymphocytes to mitogens and allogeneic cells

Lymphocytes from patients after bone marrow transplantation (BMT) are in most cases predominantly of the Leu-2+ (cytotoxic/suppressor) phenotypes and are almost unresponsive to mitogens. In contrast, normal Leu-3+-depleted, Leu-2+-enriched lymphocyte suspensions retain approximately 50% of the mitogenic response compared with that of unseparated cells. To investigate whether this discrepancy was due to active suppression, we selected nine BMT patients from whom sufficient numbers of cells were available and whose lymphocyte phenotypes were predominantly Leu-2+ after BMT. These post-BMT lymphocytes were tested for functional suppressor activities against donor and recipient pre-BMT lymphocytes in the lymphocyte transformation test. None of these post-BMT cells suppressed the response of donor or pre-BMT cells to phytohaemagglutinin A or concanavalin A. In contrast, the response of donor cells in mixed lymphocyte cultures to HLA-DR-different third-party cells was suppressed by highly X-irradiated post-BMT cells by approximately 40%. Addition of T-cell growth factor (= interleukin 2 (IL-2)) or X-irradiated donor cells to post-BMT lymphocytes partially restored the mitogenic response. These findings indicate that the early post-BMT cells lack production of IL-2 but are capable of responding to IL-2 and that the almost extinct mitogen response of these cells is due to immaturity rather than active suppression. The suppression of the allogeneic but not the mitogenic response might be explained by differences in the modes of activation; for example, the allogeneic response must involve the T-cell receptor, while the mitogenic response may not.