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Biomedical subjects

E L Ramos

Publications and source records attributed to E L Ramos.

11 recordsLinked to original sources
PubMed1992

Immunosuppression without prophylactic antilymphocyte preparations.

1. Triple-drug immunosuppression following third party transfusion can result in graft survival equal to protocols that employ prophylactic antilymphocyte preparations. 2. T1/2 was statistically improved in cadaveric and living-related donor grafts in the CsA era. 3. Patients 65 years and older had an excessive death rate. Younger groups were admixed. Extreme youth was not a risk factor. 4. Black recipients had excessive late graft loss. 5. Diabetic recipients had only a slight decline in graft and patient survival rates. 6. First and multiple graft recipients had similar transplant survival rates. 7. Delayed graft function remains costly in this immunosuppressive scheme.

Academic Medical Centers↗
PubMed1991

Ten-year experience with cyclosporine as primary immunosuppression in recipients of renal allografts.

Cyclosporine has been used as primary immunosuppression in renal allograft recipients in our unit for the past decade. The overall clinical experience and long-term effects of the agent are reviewed. There were 461 consecutive recipients of kidney grafts; 379 received grafts from cadaver donors (CAD) and 82 from living related donors (LRD). Four separate clinical protocols were used sequentially using progressively decreasing doses of CyA; azathioprine was added in group 4 recipients of LRD grafts, and in patients receiving secondary CAD grafts (group 5). The patient mortality rate was less than 5%, with sepsis being the prime contributor. The majority of kidney grafts were lost within the first 2 months after operation; those that never functioned were found almost invariably to have been irreversibly rejected. During the subsequent years of follow-up, attrition of CAD grafts was significantly greater than LRD grafts. In contrast, the attrition rate of primary and secondary CAD grafts was the same after the first 3 months, emphasizing the importance of early immunologic graft destruction. Primary nonfunction occurred in 49% of CAD kidneys and 17% of LRD grafts; however 71% of initially nonfunctioning LRD grafts never functioned at all compared to 34% of CAD grafts, the majority of such organs undergoing fulminate rejection. Individual graft loss after 1 year was almost inevitably due to chronic rejection; there were no differences in long-term allograft function among the treatment groups. Although CyA has improved overall results of kidney transplantation, chronic rejection remains a major unresolved problem.

Adult↗
PubMed1991

A randomized prospective trial of anti-Tac monoclonal antibody in human renal transplantation.

Patient entry is now complete in a prospective trial of anti-Tac, a murine IgG2a monoclonal antibody directed against the p55 chain of the human IL-2 receptor, for the prevention of renal allograft rejection. Recipients of primary cadaver allografts were randomized to receive either anti-Tac (20 mg q.d. x 10 days beginning POD 1) plus low-dose CsA (4 mg/kg/day), azathioprine (2 mg/kg/day), and prednisone (30 mg q.d.), or conventional triple therapy with CsA (8 mg/kg/day), azathioprine, and prednisone. Forty patients were entered in each group, with current followup from 6 to 26 months. The results show a significant reduction in early rejection episodes in the anti-Tac-treated patients. During the 10-day treatment, 5 of 40 anti-Tac patients had rejection episodes, compared with 21 of 40 control patients (P less than 0.001). Anti-Tac significantly delayed the time to the first rejection (12.5 +/- 6.3 vs. 7.6 +/- 6.7 days) (P less than 0.05). Despite these effects, there were no differences in either actual or actuarial graft or patient survival between the two groups. Pneumonia, primarily CMV, developed in 5 treated and 4 control patients. In patients with functioning grafts mean serum creatinine at 3 months was 1.8 +/- 0.7 in the anti-Tac group and 2.0 +/- 0.8 in the control group (P = NS); at 12 months the values were 2.3 +/- 1.5 and 1.8 +/- 0.5, respectively (P = NS). The peak expression of IL-2 receptors on circulating T-cells was significantly lower in anti-Tac patients (15.1 +/- 3.6%) than in controls (21.9 +/- 4.5%) (P less than 0.05). Seven of 10 patients tested to date developed antimouse immunoglobulin antibodies, with antiidiotype shown in 6. These antibodies do not preclude subsequent treatment with OKT3. Five patients in this and previous anti-Tac protocols have received OKT3 for acute rejection despite known pretreatment antimouse antibodies, with resolution of rejection in all cases.

Adolescent↗
PubMed1991

Recurrent diseases in the renal allograft.

Although recurrent diseases in the renal transplant are becoming increasing recognized as graft survival continue to improve, they account for less than 2 to 4% of all allograft failures. The most frequent cause of recurrent disease is recurrent glomerulonephritis. Among the recurrent glomerulonephritides, type II membranoproliferative glomerulonephritis, immunoglobulin A nephropathy, and focal and segmental glomerulosclerosis have the highest rates of recurrence. The observation continues to be substantiated that recurrence rates are increased in recipients of living-related transplants, particularly in those whose original native kidney disease was focal and segmental glomerulosclerosis, immunoglobulin A nephropathy, membranous glomerulonephritis, Henoch-Schönlein purpura, or the hemolytic uremic syndrome. Additionally, although renal transplantation has been felt to be contraindicated in patients with Fabry's disease, more recent experience with improved patient survival and decreased morbidity would suggest that transplantation may be a viable alternative for this systemic illness.

Humans↗
PubMed1989

Decrease in phenotypically defined T helper inducer cells (T4+4B4+) and increase in T suppressor effector cells (T8+2H4+) in stable renal allograft recipients.

Two monoclonal antibodies, anti-2H4 and anti-4B4, reciprocally divide the T4+ (CD4+) and T8+ (CD8+) lymphocytes into T4+2H4+, T4+4B4+, T8+2H4+ and T8+4B4+ subsets. The T4+2H4+, T4+4B4+ and T8+2H4+ subsets possess suppressor-inducer, helper-inducer, and suppressor-effector function, respectively, as previously defined in a system of B cell immunoglobulin production. Using monoclonal antibodies, including anti-2H4 and anti-4B4, and flow cytometry, we monitored lymphocyte subpopulations in 66 renal allograft recipients. We found that patients with stable allograft function have a decrease in the percentage of total T4+ lymphocytes from 41.9 +/- 9.5% pretransplant (pre-Tx) to 36.3 +/- 13.9% posttransplant (post-Tx) (P less than 0.05). This decrease was seen mainly in the T4+4B4+ or helper-inducer subset from 20.8 +/- 4.7% (pre-Tx) to 16.0 +/- 6.3% (post-Tx) (P less than 0.005). Patients with stable function were also noted to have an increase in the percentage of total T8+ lymphocytes from 21.3 +/- 10.7% (pre-Tx) to 30.9 +/- 15.4% (post-Tx) (P less than 0.02). Examination of T8 subsets revealed that a statistically significant increase was seen in the T8+2H4+ or suppressor effector subset from 15.5 +/- 9.2% (pre-Tx) to 21.5 +/- 10.2% (post-Tx) (P less than 0.01). Additionally, serial studies on 14 patients revealed an increase in the %T4+2H4+ suppressor-inducer subset from 9.31 +/- 3.64% (pre-Tx) to 15.71 +/- 6.41% (post-Tx) (P less than 0.0025). Since the role of these subsets has not been established in alloimmunity, in vitro allogeneic studies of 2H4-enriched (2H4+) and 2H4-depleted (2H4-) lymphocytes from normal peripheral blood were performed. In the mixed lymphocyte reaction, 2H4+ cells proliferated less than 2H4- cells (cpm ratio 2H4+/2H4-: 0.63-0.84), but 2H4+ cells generated twice as much suppressor activity as 2H4- cells (ratio % suppression 2H4+/2H4-: 1.9-2.3). These results suggest that 2H4+ cells play a role in the suppressor limb of the alloimmune response and that the increase in cells of this phenotype in our transplant population may be responsible for the maintenance of stable allograft function.

Adult↗
PubMed1989

Differential IL-2 receptor expression in renal allograft recipients treated with an anti-IL-2-receptor antibody.

Patients were entered into a randomized trial of prophylaxis for renal allograft rejection by the administration of an anti-human IL-2 receptor antibody, anti-Tac, during the first ten days posttransplant. Interleukin-2 receptor (IL-2 R) expression was measured using two anti-IL-2 R monoclonal antibodies (moAbs), anti-Tac and 1HT4-4H3. These two antibodies recognize closely spaced epitopes on the 55 kD chain of the IL-2 R. IL-2 R expression was examined on peripheral blood small lymphocytes in three groups of patients who received: (A) cyclosporine CsA and prednisone for baseline immunosuppression (n = 9); (B) anti-Tac with CsA and prednisone as baseline immunosuppression (n = 12); and (C) anti-Tac with azathioprine and prednisone as baseline immunosuppression (n = 5). We found that large numbers of T cells express IL-2 receptors despite the presence of anti-Tac (average of IL-2 R-positive cells at day of peak IL-2 R expression 56.0 +/- 20.8% in group A, 65.2 +/- 26.6% in group B, 21.0 +/- 7.4% in group C). IL-2 R expression did not correlate with clinical activity, and the presence or accessibility of epitopes on the same 55 kD chain varied dramatically from patient to patient.

Antibodies, Monoclonal↗
PubMed1989

Prophylactic use of monoclonal anti-IL-2 receptor antibody in cadaveric renal transplantation.

In vivo administration of an anti-interleukin-2 (anti-IL-2) receptor monoclonal antibody is a potential new therapy for prevention of allograft rejection of a freshly transplanted organ. Such an approach is more selective than targeting all T cells, or even the CD4 or CD8 major subsets, because only the very recently activated cells should be affected. A clinical trial of anti-Tac monoclonal antibody is in progress in which 20 mg of the immunoglobulin G 2a (lgG2a) antibody is administered intravenously daily for 10 days after cadaveric renal transplantation. Combinations with and without azathioprine, and with varying doses of cyclosporine with prednisone, are being evaluated in a randomized trial. Results to date show a significant immunosuppressive effect of anti-Tac, as measured by a reduced incidence and later onset of acute rejection episodes compared with cyclosporine plus prednisone or cyclosporine plus azathioprine plus prednisone. Removal or cytodestruction of IL-2-receptor positive cells from the peripheral blood does not occur to any major degree, even though serum levels of the antibody are always detectable. In addition, functional studies of MLR, CML, and suppressor cell generation 4 days after cessation of anti-Tac administration show no significant difference between treated and control groups The effect of anti-Tac seems, therefore, to be limited to inhibition of IL-2-mediated T-cell growth during the period of administration, with recovery after a few days' lag period.

Antibodies, Monoclonal↗
PubMed1987

Antigen specificity of mixed lymphocyte response-induced suppressor cells.

The nature of the antigens recognized by mixed lymphocyte response-generated suppressor cells is currently unknown. Previous investigations have yielded conflicting results, with different studies finding that suppressor cells recognize HLA class I antigens, class II antigens, or neither. To characterize the antigens recognized by suppressor cells (modulators) further, we generated 36 different modulators and assayed them for suppressor activity against a random 48-member HLA-typed panel in a total of 473 assays. Logistic regression analysis of the data revealed that suppression was correlated with B and DQ antigenic sharing between the original stimulator (used to generate the suppressor cells) and the test culture stimulator (p = 0.0043 and 0.0277, respectively). A role for DR antigen sharing could not be excluded. Overall, 35% of all suppressed assays could not be accounted for by the sharing of either any classical private HLA antigens, or of HLA-A or B locus cross-reactive group specificities. Suppression in these instances may involve the sharing of minor antigenic determinants, unidentified private HLA epitopes, or possibly another gene related to suppression that exists in linkage disequilibrium with the HLA-B locus or the DQ subregion.

Cross Reactions↗