The effects of anti-CD2 antibodies on the differentiation of mouse thymocytes.

Using a rat monoclonal antibody against mouse CD2, we determined the expression of this marker on thymocytes during ontogeny. CD2 expression becomes detectable at day 15 and reaches adult levels (approximately 95% positivity) by day 19. Furthermore, the effect of anti-CD2 antibodies on T cell differentiation was analyzed by addition of antibodies to thymus organ cultures or repeated injection into newborn mice. Anti-CD2 antibodies inhibit CD2 expression in organ cultures and drastically reduce its expression on thymocytes and peripheral lymphocytes in vivo. In either situation, suppression of CD2 expression does not significantly alter the generation of T cells expressing CD3, CD4, CD8 and T cell receptor V beta 8. These results do not support a role for CD2 in early steps of thymocyte differentiation.