Objective—To evaluate effects of cyclosporine, dexamethasone, and the immunosuppressive agent human CTLA4-Ig on cytokine production by feline lymphocytes in vitro and to assess patterns of cytokine production for 5 immunosuppressed renal transplant recipient cats.
Animals—21 clinically normal cats and 5 immunosupressed renal transplant recipient cats.
Procedures—Peripheral blood mononuclear cells were isolated from clinically normal cats and stimulated with concanavalin A (Con A; 10 μg/mL) alone or Con A with cyclosporine (0.05 μg/mL), dexamethasone (1 × 10−7M), a combination of cyclosporine-dexamethasone, or human CTLA4-Ig (10 g/mL). Cells from transplant recipients were stimulated with Con A alone. An ELISA was performed to measure production of interferon (IFN)-γ, granulocyte macrophage–colony stimulating factor (GM-CSF), interleukin (IL)-2, IL-4, and IL-10. Proliferation of CD4+ and CD8+T cells from immunosuppressed cats were also evaluated. Pairwise comparisons were performed via a Wilcoxon signed rank test or Wilcoxon rank sum test.
Results—Cyclosporine, dexamethasone, cyclosporine-dexamethasone combination, and CTLA4-Ig caused a significant decrease in IL-2, IFN-γ, and GM-CSF production. Cyclosporine and cyclosporine-dexamethasone, but not human CTLA4-Ig, caused a significant decrease in IL-10 production. High basal concentrations of IL-2 and IL-10 were identified in transplant recipients, and IL-10 was significantly increased in stimulated cultures. In immunosuppressed cats, there was a decrease in frequency of responders and proliferative capacity of CD4+ and CD8+T cells.
Conclusions and Clinical Relevance—CTLA4-Ig successfully inhibited proinflammatory cytokines while sparing cytokines critical for allograft tolerance. These data may be useful for developing better strategies to prevent rejection while sparing other immune functions.
Objective—To determine whether human CTLA4-Ig
([hu]CTLA4-Ig) inhibits costimulation-dependent lymphocyte
proliferation in vitro, compare the effects of
(hu)CTLA4-Ig with cyclosporine and steroids on CD4+
and CD8+ T-cell lymphocyte proliferation, and determine
whether memory T-cell function remains intact
in the presence of (hu)CTLA4-Ig.
Procedure—Peripheral blood mononuclear cells
(PBMCs) were stimulated with concanavalin A (costimulation-
dependent mitogen) or phorbol 12-myristate
13-acetate and ionomycin (costimulation independent
mitogens) alone or in the presence of
(hu)CTLA4-Ig, cyclosporine, or dexamethasone;
effects of these treatments on lymphocyte proliferation
were assessed by incorporation of thymidine
labeled with tritium or flow cytometry. Antigen-specific
proliferation was determined by stimulating
PBMCs from 2 healthy cats seropositive for
Toxoplasma gondii with soluble Toxoplasma antigen
alone or in the presence of (hu)CTLA4-Ig or
Results—(hu)CTLA4-Ig inhibited costimulationdependent
lymphocyte proliferation in vitro but had
no effect on costimulation-independent lymphocyte
proliferation. Compared with mitogen alone,
(hu)CTLA4-Ig caused a significant decrease in responder
frequency and proliferative capacity of CD4+ T
cells; however, the effect on CD8+ T cells was not significant.
Cyclosporine alone or with dexamethasone
had a significantly greater suppressive effect on
responder frequency and proliferative capacity of
CD4+ and CD8+ T cells, compared with (hu)CTLA4-Ig.
Compared with cyclosporine, (hu)CTLA4-Ig appeared
to have a sparing effect on antigen-specific proliferation
of memory CD4+ and CD8+ T cells.
Conclusions and Clinical Relevance—(hu)CTLA4-Ig
selectively inhibited costimulation-dependent proliferation
of lymphocytes in vitro and had a sparing effect
on antigen-specific proliferation of memory cells. The
specificity of its mechanism of action suggests that
(hu)CTLA4-Ig may prevent allograft rejection but leave
memory responses to previously encountered antigens
intact. (Am J Vet Res 2005;66:483–492)