Analysis of the function of L3T4+ T cells by in vivo treatment with monoclonal antibody to L3T4.

We have used MAb to L3T4 to examine the function of L3T4+ T cells in normal and autoimmune mice. Treatment of mice with MAb to L3T4 profoundly depleted L3T4+ cells from the blood, spleen, and lymph nodes, but not the thymus. In BALB/c and C57BL/6 mice, selective depletion of L3T4+ cells blocked both primary and secondary humoral immune responses and inhibited, but did not prevent, cellular immune responses. In lupus-prone B/W and BXSB mice, depletion of L3T4+ cells significantly retarded autoimmune disease. Because the L3T4 antigen in mice is homologous to the CD4 antigen in humans, these findings have implications regarding the function of CD4+ T cells and the prospects for using MAb to CD4 as therapeutic agents.