Differential Regulation of Human, Antigen-specific Th1 and Th2 Responses by the B-7 Homologues, CD80 and CD86

A selectivity of B7.1 (CD80) for promoting Th1 responses and B7.2 (CD86) for promoting Th2 responses in the murine system has recently been suggested. The present study explores this hypothesis, using human PBMCs and antigen-specific Th1 and Th2 clones. Proliferative responses of peripheral blood mononuclear cells (PBMCs) from ragweed-allergic, tetanus toxoid-immunized individuals were downregulated by treatment with anti-CD86 in ragweed- and tetanus toxoid-driven cultures (% Inhibition = 55 ± 4 and 61 ± 12, respectively; P < 0.03 relative to untreated cultures). Gene expression in PBMCs for interleukin (IL)-4, IL-5, and Interferon γ (IFNγ), assessed by reverse-transcriptase polymerase chain reaction, was also downregulated by treatment with anti-CD86 in both the ragweed- and tetanus toxoid-driven systems. Neither independent efficacy nor synergy with anti-CD86 was apparent with anti-CD80 treatment; two different anti-CD80 blocking antibodies yielded identical results. Conversely, antigen-specific Th1 and Th2 clones were insensitive to treatment with either anti-CD80, anti-CD86, or a combination of the two. Unaffected parameters included proliferative response (P < 0.14 and 0.33, respectively, for Th1 and Th2), proinflammatory cytokine gene expression, and cytokine protein secretion into culture supernatants (P < 0.44 and 0.16, respectively, for IL-4 and IFNγ). We conclude that CD86 is the primary B7 signaling homologue in human PBMC responses, and that second signal pathways through the B7 homologues have no effect on phenotypically differentiated T helper cells in humans.