T. Mohanakumar

Cyclosporine in Cardiac Transplantation

Cyclosporine is a new immunosuppressive drug that acts early in the exposure of a host to allogeneic stimulation. It is a peptide of fungal origin. It has selective action on T cells, leaving the other cells of the immune system intact. It acts by preventing the function of the early activation signals of T cells, such as the acquisition of receptors for Il 2 and Il 1. It is lipophilic, moderately well absorbed by the gut, and metabolized by the liver. Factors affecting absorption or hepatic metabolism alter the amount of cyclosporine available in the circulation. Circulating levels can be measured by radioimmunoassay or HPLC. Doses should be tailored to trough levels taken approximately 12 hours after an oral or intravenous dose or to individual pharmacokinetic curves. The drug is nephrotoxic, hepatotoxic, and neurotoxic. In addition, cyclosporine has been associated with hypertension, hemolytic-uremic syndrome, increased incidence of intravascular thrombotic events, hypertrichosis, gum hyperplasia, pericardial effusion, and lymphoproliferative disorders. Despite these complications, cyclosporine usage seems to have improved short-term cardiac allograft survival and to have reduced the complications associated with side effects of steroids. As a result, cyclosporine has spawned a resurgence of interest in cardiac transplantation, which will be of great benefit in prolonging the lives of patients with end-stage cardiac disease.

THE IMPORTANCE OF THE LEWIS SYSTEM IN CADAVER RENAL TRANSPLANTATION

Previous reports have suggested that Lewis (Le) antigens may exert a significant effect on cadaver renal allograft (CRA) survival, especially in black recipients in whom there is a higher frequency of Le-negative phenotypes. We review our experience with this problem in 70 donor-recipient pairs of CRA who underwent prospective Le typing and received conventional immunosuppression between 1980 and 1983 Recipient typing alone yielded the following graft survival ((IS) and patient survival (PS) at 2 years by life table analysis: (a+,b;-_) (n = 12) 51% GS, 937c PS; (a-,b+) (n = 44) 57% GS, 88% PS; and (a-,b;-) (n = 14) 51% GS, 93% PS(P-ns for GS, PS). Recipient racial characteristics did not effect ultimate graft survival, as whites and blacks had similar two-year GS in all phenotypic groups. When Le matching was considered, no significant differences in one-year graft survivals could be ascertained between Le-matched and Le-mismatched donor-recipient pairs, and this effect persisted despite stratification for race and HLA-A.B and DR histoincompatibilities In light of these results, we do not recommend using Lewis compatibility as a criterion for donor selection in cadaver renal allografting, as this substantially increases the difficulty in finding suitable matches, especially in the (a-,b-) recipient group

Lack of association of human renal allograft rejection and circulating K-cell, NK-cell, or total T-cell levels

Abstract Thirty-three recipients of cadaveric renal allografts and four living-related allografts were serially monitored at weekly intervals for natural killer (NK)-cell, effector-cell (K) activity in antibody-dependent cellular cytotoxicity (ADCC) and daily total circulating T-lymphocyte (TCTC) levels. Rabbit anti-human thymocyte globulin (ATG) was shown to have a dramatic suppressive effect on all three immune parameters in most of the patients (>90%) studied. Patients experiencing rejection episodes during the first 60 days post-transplant did not express increased levels of any parameter compared to seven non-rejecting patients when measured pretransplant or after 2 and 4 weeks post-transplant. Furthermore, increased early levels were not associated with an increased frequency of rejection episodes. Values of each of these parameters measured during clinical rejection were shown not to be significantly elevated when compared to values determined at identical times post-transplant in recipients who experienced no rejection episodes during the initial 60 days following grafting. Similar comparisons made 3, 2, and 1 week prior to rejection episodes also failed to reveal a significant elevation of any parameter in advance of rejection. Thus, NK-cell, K-cell, and TCTC levels do not appear to be associated with rejection phenomena and are of limited clinical usefulness in monitoring renal allograft recipients.

In vitro evidence for defective afferent immune function in long-term renal allograft recipients.

Experiments were designed to evaluate afferent immune functions in 21 long-term (greater than or equal to 3 years) renal allograft recipients by using in vitro assays that included autologous and allogeneic mixed lymphocyte reactions (AMLR and allo-MLR), proliferative responses to a soluble antigen (tetanus toxoid), and the ability to generate cytotoxic T lymphocytes (CTL) following stimulation in an AMLR. The results showed that allograft recipients generated responses in the allo-MLR (means = 84,789 +/- 8242) that were comparable to those exhibited by normal controls (means = 86,082 +/- 7423). Likewise, mean responses in the AMLR were similar in recipients and controls (14,937 +/- 3243 versus 16,101 +/- 3005), although a greater percentage of recipients generated AMLRs below 5000 cpm than did normals (8/21 versus 4/20). However, 13 recipients analyzed for responsiveness to tetanus toxoid were shown to generate mean proliferative responses that were significantly depressed below normal (18,095 +/- 5545 versus 48,935 +/- 8813, P less than 0.001). Furthermore, despite significant proliferation in the AMLR means = 27,648 +/- 5168), 8 recipients generated significantly lower CTL activity in AMLR cultures than normal controls (mean percentage of cytotoxicity = 10.3 +/- 4.7 versus 24.9 +/- 4.7, P less than 0.05). These recipients generated normal CTL levels against allogeneic target cells following stimulation in an allo-MLR. Thus, these studies provide experimental support for the existence of altered T helper cell-mediated functions in long-term renal allograft recipients.

Potentiating effect of HLA matching and blood transfusion on renal allograft survival.

An analysis of HLA (A and B) recipient-donor matching on the outcome of 105 cadaver kidney transplants performed at the Medical College of Virginia transplant center revealed that there is a significant, overall difference (P = 0.03) between recipients receiving kidneys mismatched at two or less HLA loci versus recipients mismatched at three or more loci, the fewer mismatch category showing a better graft survival. The effect of blood transfusion prior to transplantation was studied and found to improve the outlook, especially in the best matched groups. The number of transfusions does show a significant effect (P = 0.04) in the subgroup of patients with two or less mismatches, but for patients with three or more mismatches, the number of transfusions does not seem to matter (P = 0.83). However, in this study even the allografts mismatched at three or more loci had a 1-year graft survival of greater than 65%, indicating that factors other than HLA or blood transfusion play significant roles in the graft outcome. Although the findings are based on a somewhat small number of patients, the statistical significance suggests a potentiating effect of HLA matching and blood transfusion on renal allograft survival.

Detection and localization of an extra HLA locus in a karyotypically normal male by chromosomal in situ hybridization

The codominant expression of three HLA haplotypes was found in a healthy 21‐year‐old Black male, whose prometaphase karyotype was normal by light microscopy. He was the sibling of an antenatally diagnosed female fetus with a partial duplication of 6p. The duplication arose from a complex presumably balanced maternal chromosome rearrangement: 46, XX, dir ins(14;6)(14pter→14p11::6p22→6p21.1::14p11→14qter;6pter→6p22::6p21.1→6qter). Chromosomal in situ hybridization using a tritium‐labeled genomic clone corresponding to a class I HLA gene revealed two sites of hybridization: at 6p21.3, the band to which this probe has been assigned in normal individuals (Morton et al. 1984a) and a second site at 6p11. We postulate that a recombinational event during meiotic pairing in the mother led to the reintroduction into the normal chromosome 6 homolog of a small segment of the original insertion in chromosme 14 which contained the HLA‐A and ‐B determinants.

T-Lymphocyte Analysis in Cardiac Allograft Recipients Treated with Cyclosporine

To assess the usefulness of circulating T-lymphocyte analysis in cardiac transplantation, T helper (Th) and T suppressor-cytotoxic (Ts-c) subsets were serially monitored in 33 cardiac allograft recipients treated with cyclosporine. The short-term prognosis of their 47 treated rejection episodes were retrospectively correlated with the changes in T-cell subpopulations. The data indicate three main findings. Reversed Th to Ts-c ratio (less than 1) was associated with a reduced incidence of rejection onset and a benign clinical course after treatment for rejection. Reversed Th:Ts-c ratio caused by antirejection therapy was associated with less chance of recurrence during the rest of hospitalization, regardless of the mode of therapy and irrespective of whether the rejection was primary or recurrent. These changes were mainly mediated by a reduction in T helper cells rather than changes in the T suppressor-cytotoxic subset or total T cells. Titration of antirejection therapy based on these T-cell dynamics may reduce either overtreatment or undertreatment. A prospective randomized study seems warranted to evaluate this approach as an alternative to a predetermined antirejection protocol.

Pretransplant warm B cell antibodies in recipients of primary and retransplanted cadaver renal allografts.

Eighty-four recipients of cadaveric renal allografts were retrospectively crossmatched for donor-specific pretransplant B cell antibody. Of these, 28 were found to be positive for the antibody and 56 were negative. Actuarial survival analysis over six years revealed a slightly better graft survival overall in the B-cell-negative group as compared with the B-cell-positive group (P<0.07). These patients were further subgrouped into those who received primary transplants and those who were retransplanted. Fifty-four percent of the B-cell-positive group (15/28) consisted of retransplants, and only 13% (7/56) of the B-cell-negative group were retransplants. When considering primary transplants only, B-cell-negative and B-cell-positive groups had similar graft survival rates (P<0.25). When retransplants only were considered, the graft survivals of the B-cell-positive and B-cell-negative groups were comparable (P<0.32). The most significant differences were observed when comparing the B-cell-positive primary transplant group with the B-cell-positive retransplanted group. The primary transplants fared consistently better at all time intervals (P<.007). Conversely, when primary and retransplants in the B-cell-negative group were compared, no differences were noted (P<0.29). Our results suggest that the identification of pretransplant B-cell antibodies may be indicative of a poorer allograft survival prognosis in patients who have been previously transplanted.

Class I antibody induction by rat endothelium

Supradiaphragmatic vein grafts were transplanted from ACI (RT1a) to Fisher (RT1(1)) rats to determine whether the endothelium and/or circulating passenger leukocytes were necessary for the induction of an antibody response. Vein grafts from immunosuppressed and irradiated donors induced lymphocytotoxic and hemagglutinating antibody in recipient rats. In addition, IgG antibody produced in Fisher recipients was found by indirect immunofluorescence to donor endothelium. When the endothelium was removed from donor veins either by collagenase or by scraping the intima, no antibody resulted after transplantation. The lymphocytotoxic and hemagglutinating antibodies and the antibodies identified by indirect immunofluorescence were removed by absorbing the Fisher serum in ACI red blood cells. The endothelium seems to be capable of inducing Class I antibodies when allogeneically transplanted as vein grafts.