Use of monoclonal antibodies to T-cell subsets for immunologic monitoring and treatment in recipients of renal allografts

Patients with abnormal proportions of T-lymphocyte subsets have reduced in vitro cellular immunity

Monoclonal antibodies which identify helper/inducer (OKT4) and cytotoxic/suppressor (OKT8) subsets of human T lymphocytes have recently been used to investigate immunoregulation in isolated cell populations, as well as in human disease states. However, the relationship between relative proportions of OKT4- and OKT8-positive blood lymphocytes and in vitro cellular immune function in patients with immunodeficiencies has not been studied extensively. We enumerated T-lymphocyte subsets with OKT4 and OKT8 antibodies, and measured proliferative responses to allogeneic cells in mixed lymphocyte culture (MLC) and to phytohemagglutinin (PHA), in peripheral blood mononuclear cells (PBMCs) from 60 patients with varying degrees of immunodeficiency and 20 healthy controls. Controls had 56.0 +/- 5.3% (mean +/- 1SD) OKT4-positive lymphocytes, 28.6 +/- 5.9% OKT8-positive lymphocytes, and an OKT4/8 ratio of 2.05 +/- 0.55. We defined as abnormal values of less than 40% OKT4-positive or greater than 45% OKT8-positive lymphocytes (3 SD below and above mean values, respectively), or an OKT4/8 ratio of less than 1.2. Patients with these abnormal percentages of T-lymphocyte subsets had significantly lower mean MLC and PHA responses (P less than 0.001), and higher incidences of abnormal MLC and PHA responses (P less than 0.01). Abnormal proportions of T-lymphocyte subsets correlated with low MLC and PHA responses in most immunodeficient patients, although some patients with low MLC and PHA responses had normal subset distributions. T-Cell subset proportions were heterogeneous among patients with the same diagnosis.

Inhibitors of renin: present and future

Four classes of compounds have been demonstrated to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogs of angiotensinogen and peptides that are related to the amino-terminal sequence of renin's precursor (Pro-renin). With the purification of renin, specific polyclonal or monoclonal antibodies have become available. The former have already been used extensively in physiologic studies in intact animals. Pepstatin is an inhibitor of many acid proteases. Its in vivo application has been retarded by its relative insolubility, but recent chemical modifications, particularly the addition of charged amino acids at the carboxy-terminus have rendered it more useful. The minimal substrate for renin is an octapeptide segment of the protein substrate: His-Pro-Phe-His-Leu-Leu-Val-Tyr. Variants of this sequence have resulted in competitive inhibitors that are useful in vivo. Recently, remarkably active inhibitors have been synthesized by reducing the peptide bond that is cleaved by renin, producing what may be a transition state inhibitor. Several of these peptides have been shown to be effective as in vivo inhibitors of the hypertensive effect of the enzyme. The development of inhibitors based on Pro-renin sequences are awaited with interest.

Protective human hybridoma antibody to tetanus toxin

Postimmunization human B lymphocytes and mouse myeloma cells were fused to produce interspecies hybridomas secreting human antibody of predefined specificity with an initial frequency comparable to intraspecies fusion. After 13 mo in culture, one clone continued to secrete high titers of human IgG antitetanus toxin antibody. This antibody binds to the B fragment of tetanus toxin and protects mice against tetanus. The demonstration of in vivo protection with a human monoclonal antibody is an important first step towards the ultimate goal of human administration of monoclonal antibodies for the prevention and therapy of human infections.

Reversible alterations in immunoregulatory T cells in smoking. Analysis by monoclonal antibodies and flow cytometry

We characterized T-lymphocyte subsets in peripheral blood of smokers (N = 60) and nonsmokers (N = 35). Total T-lymphocytes and T cell subsets were similar to nonsmokers in light and moderate smokers. In heavy smokers, total OKT3+ cells were increased, the percentage of OKT4+ cells was decreased, and percentage and total number of OKT8+ cells were increased. The ratio of OKT4+ to OKT8+ lymphocytes was decreased in heavy smokers. The percentage of OKT8+ cells and the OKT4+/OKT8+ ratio returned to normal in heavy smokers six weeks after they stopped smoking. These findings suggest that cigarette smoking causes reversible alterations in immunoregulatory T cells.

Human in vivo antigenic modulation induced by the anti-T cell OKT3 monoclonal antibody

The anti-pan T cell monoclonal antibody OKT3 was administered daily for 2 weeks in four human renal allograft recipients. The antibody induced a dramatic and immediate depletion of peripheral T cells followed by an in vivo antigenic modulation of the OKT3-defined membrane antigen: after three injections, OKT3-treated patients showed a limited but significant number of OKT3- cells of T cell nature (as defined by OKT4 and OKT8) which recovered the OKT3 receptor after an overnight in vitro incubation in the absence of the monoclonal antibody.

Immunology of renal transplantation rejection

Recent studies into the mechanisms of graft rejection have highlighted the complexity of this response. Although current immunosuppressive treatments are crude, laboratory observations on the mechanisms of graft rejection have already led to various techniques which may assist in the early diagnosis of rejection, in the prognosis of a rejection episode, and in the development of more specific therapy to prevent and treat rejection. Already, the monitoring of T-cell subsets in blood and graft infiltrates is of considerable help. These observations may lead to the advent of more specific and subtle immunosuppressive therapy, such as the use of monoclonal antibodies directed against T-cell subsets. In the long term, the induction of states of specific unresponsiveness to the graft holds great promise, as do the development of techniques to assess adequacy of immunosuppression and to detect the presence of specific unresponsiveness.

Long-term survival after cadaveric renal transplantation

In a series of 404 consecutive first cadaver kidney transplants performed since 1967 the actuarial five- and 10-year survival of patients were 61% and 47% respectively and of grafts 46% and 36%. In more than four-fifths of the patients surviving these intervals the original cadaveric grafts were functioning at these times, and most of the remainder were sustained by subsequent grafts. Although graft survival has remained static since 1967, patient survival improved. Results for 43 consecutive second cadaver transplants were similar after five years to those of first grafts. These results promote the acceptability of cadaveric transplantation as a long-term treatment for chronic renal failure.

Reduction of the fraction of circulating helper-inducer T cells identified by monoclonal antibodies in psoriatic patients treated with long-term psoralen/ultraviolet-A radiation (PUVA)

Ultraviolet radiation has been found to alter the distribution and function of human lymphocytes. To determine whether photochemotherapy (PUVA) alters circulating levels of T cell subset marker-bearing lymphocytes, cells from 9 patients with psoriasis undergoing PUVA therapy for several years (mean 4.6 +/- 1.4 yr), 17 patients with active untreated psoriasis, and 20 healthy volunteers were reacted with monoclonal antibodies to T cell surface markers, including OKT3 (all peripheral blood T cells), OKT4 (helper/inducer T cells), OKT6 (common thymocytes), and OKT8 (suppressor/cytotoxic T cells), and analyzed by flow cytometry. There were no differences in the distribution of T cell subsets between healthy volunteers and patients with active psoriasis. In contrast, the percentages of lymphocytes reacting with OKT3 and OKT4 were lower (by 16% and 12% percent respectively, p less than 0.0025) in the PUVA-treated patients compared to healthy volunteers or patients with active psoriasis that had not received PUVA therapy. There was no difference in the percentage of OKT8 and OKT6 bearing cells. Squamous cell carcinoma of the skin subsequently developed in 2 of 3 PUVA-treated patients with the lowest percentages of T4-bearing cells. These findings indicate that long-term PUVA therapy is associated with a reduction in circulating helper/inducer T cells. This reduction may have a role in the altered immune function reported in PUVA-treated patients.

The improving utility of renal transplantation in the management of end-stage renal disease

The results achieved by treating patients with end-stage renal failure with allotransplantation have improved dramatically since the 1950s when immunosuppression was induced by total body irradiation and there was a lack of HLA typing. Although long-term hemodialysis offers prolonged survival and partial rehabilitation for many individuals with end-stage renal disease, the technique is inconvenient and time consuming. Patients are restricted by necessary proximity to the machine, dietary limitations, potential failure of access sites, and complications of various organ systems. Despite the availability of dialysis and the federal funds to partially pay for treatment, long-term dialysis still remains a costly process for the individual in need of care. During the same period when dialysis techniques improved and became widely available, transplantation of the human kidney became an established and justified treatment for some patients with end-stage renal disease. Those with successful kidney allografts may achieve remarkable recovery and are often able to return to normal lives. One of the more striking improvements in the results of renal transplantation in recent years had been the decline in morbidity and mortality. Mortality by the end of the first year after transplantation during which time most deaths occur, is currently less than 5 percent in a number of major medical units. In part, this decline represents a change in philosophy by transplant teams, who now tend to decrease immunosuppression and sacrifice the kidney rather than the patient in instances of inexorable rejection. In addition, declining mortality is directly attributable to improved methods of preventing, discovering, and treating patients with potential or real infections. More recently, in some centers, the rate of successful engraftment has shown gratifying improvement due to refinements in tissue typing, improved cross matching, new immunosuppressive therapies, and pretransplant conditioning with blood products. These recent improvements are the primary focus of this review. Unfortunately, until very recently, rates of functional survival of allografts have not been satisfactory.

Neuroimmunology I: Immunoregulation in neurological disease

Aberrations in immune function that ultimately result in disease states may involve three aspects of immune regulation: (1) regulatory T cells, which both suppress and induce immune responses; (2) idiotype-antiidiotype networks, which serve as internal regulatory networks during generation of an immune response; and (3) immune response genes, which determine genetic differences in an individual's immune response. Three major diseases of the nervous system, multiple sclerosis, myasthenia gravis, and acute inflammatory polyneuropathy (Guillain-Barré syndrome), are classified as "autoimmune" in nature and may be due to underlying disorders of immunoregulation. In multiple sclerosis there is a loss of suppressor T cells in the peripheral blood during attacks, in myasthenia gravis there are thymic abnormalities and antibodies against the acetylcholine receptor, and in acute inflammatory polyneuropathy, macrophage-mediated destruction of peripheral nerve myelin occurs in the context of sensitized T cells and is usually associated with a preceding viral illness. In each of these diseases the following central questions must be answered: (1) against what antigen (or antigens) of the nervous system is the autoimmune response directed? (2) what is the mechanism of immune damage? and (3) what initiates, or triggers, the autoimmune response?

Elimination of T-lymphocytes from human bone marrow with monoclonal T-antibodies and cytolytic complement

Complement-mediated cytolysis has been used to remove T-lymphocytes from suspensions of human peripheral blood and bone marrow. Selective T-cell removal was investigated by three monoclonal antibodies. OKT3, MBG6 and OKT11A. All three removed greater than 90% of T-cells but combinations were necessary to kill greater than 99% of T-cells in vitro. The macrophage-granulocyte and erythroid colony forming cells of the bone marrow were spared. The method can be applied on bulk BM samples during clinical BM transplantation and will be useful to establish whether the virtually complete removal of T-lymphocytes totally prevents transplant associated graft-versus-host disease in man.

Interstitial mononuclear cell populations in renal graft rejection. Identification by monoclonal antibodies in tissue sections

The interstitial mononuclear cell populations of 22 renal grafts with interstitial rejection (IR), 6 grafts with interstitial nephritis without rejection (IN), and 5 kidneys without infiltration (3 donor kidneys, 2 grafts) were identified and quantitated by monoclonal antibodies recognizing T cells (TA-1, OKT3), helper inducer cells (OKT4), cytotoxic/suppressor cells (OKT8), B cells (BA-1), and monocytes and null cells (OKM1). Double-layer fluorochrome enhancement using F(ab')(2) reagents and nuclear counter staining with ethidium bromide enabled quantitation of the number of positive mononuclear cells, interstitial cells, and total cells on each of 30-55 microscopic fields per tissue section. T cells were the most abundant infiltrating cell in tissues with IR (35 +/- 9.8 percent), significantly higher than that seen in IN (21 +/- 16 percent) or in kidneys without infiltration (5.0 +/- 3.9 percent). The percentage of T cells identified by TA-1 or OKT3 was approximately equivalent to the summation of OKT4 plus OKT8. Although no differences were observed in the percentage of OKT4 cells, the percentage of OKT8 was significantly higher in IR (26 +/- 7.7 percent, P {less than} 10(-4)) than in IN (9.3 +/- 6.2 percent) or in kidneys with normal interstitium (3.0 +/- 2.4 percent). The ratio of OKT8/OKT4-positive T cells in 22 graft tissues with IR (3.2 +/- 1.4) was greater (P {less than} 0.0007) than 6 graft tissues with IN without rejection (0.82 +/- 0.39) and the 5 kidney tissues without interstitial infiltration (0.75 +/- 0.25). There was no significant difference between the groups in the relatively low percentage of interstitial cells identified as B cells reacting with BA-1 or containing S(IgD,M). The percentage of interstitial cells recognized by OKM1 was similar in rejection and interstitial nephritis, with both being greater than controls (P {less than} 0.02). The relative numbers of blood mononuclear cells identified by the monoclonal antibodies was generally not predictive of the proportions present in kidney tissue, although OKT4-positive blood cells were less numerous and OKMI+ blood cells were more numerous than in controls (P {less than} 0.002). Quantitative analysis of identifiable interstitial cells in graft rejection reveals that most infiltrating cells are T cells, the greater proportion of which are recognized by OKT8. OKT8-positive cells may play an important role in mediating renal graft rejection.

Treatment with anti-Ia and antiblast/monocyte monoclonal antibodies can prolong skin allograft survival in nonhuman primates

Two monoclonal antibodies, one directed against human Ia antigens and the other reactive to both monocytes and blast cells, were evaluated for prolonging skin graft survival in Rhesus monkeys. Various doses of the antibodies were given intravenously until the skin graft was rejected. Compared with a graft survival of five days for untreated control monkeys, five animals receiving anti-Ia had grafts surviving from 13 to 19 days and six animals treated with antiblast/monocyte antibody had grafts surviving from 15 to 22 days. No adverse side effects were seen with treatment with antiblast/monocyte antibodies. However, the dose of anti-Ia antibody was critical in that four monkeys died of anaphylaxis when injected with amounts exceeding 200 microliters of ascites with a titer of 1:10(5).

The measurement of leukocyte subsets in the peripheral blood of cancer patients with solid tumors using monoclonal antibody reagents

Monocyte and lymphocyte subsets were quantitated in the peripheral blood of normal subjects and patients with solid tumors using the monoclonal antibody reagents OKM1, BRL63D3, OKT3, OKT4, and OKT8. Percentages and numbers of cells reacting with monoclonal reagents were analyzed by indirect immunofluorescence. Correlations between leukocyte subset values and stage of disease or immunocompetence were sought. No differences from normal were seen in the percentage of OKT3, OKT4, and OKT8 cells or in the ratios of OKT4/OKT8 cells in peripheral blood mononuclear cells (PBMC) from all cancer patients, patients with localized disease, or patients with advanced disease. A significant decrease in absolute numbers of lymphocytes, OKT3 cells, OKT4 cells, and OKT8 cells was seen in the peripheral blood of patients with advanced disease reflecting the absolute lymphopenia of these patients. A significant increase was seen in the percentages of PBMC reacting with OKM1 and BRL63D3 from patients with advanced disease compared with normal donors or localized disease patients. A positive correlation was found between PHA responsiveness and absolute numbers of OKT3 and OKT4 cells. A negative correlation was found between PHA responsiveness and percentages of OKM1 cells. These data indicate that malignant disease does not alter T cell subset percentages in patient peripheral blood but may decrease their absolute numbers in association with absolute lymphopenia. On the other hand, percentages of OKM1 and BRL63D3 cells are increased in patients with advanced solid tumors in association with impaired PHA responsiveness.