Treatment with Depleting CD4 Monoclonal Antibody Results in a Preferential Loss of Circulating Naive T Cells but Does Not Affect IFN- g Secreting TH1 Cells in Humans

CD4 pos TH1 T cells are considered to play a central role in a number of human autoimmune diseases such as rheumatoid arthritis (RA) and multiple sclerosis. Experimental treatment protocols aimed at selectively eliminating CD4 pos T cells thus far have yielded disappointing clinical results. Here we analyzed phenotype and function of circulating T cells in multiple sclerosis patients treated with the chimeric CD4 mAb cM-T412 in a randomized, double-blind, placebo-controlled, magnetic resonance imaging–monitored phase II trial. Treatment resulted in a long-lasting depletion of CD4 pos T cells but did not affect CD8 pos T cell numbers. Analysis of CD4 pos subpopulations showed that unprimed, CD45RA pos / R0 neg lymphocytes were approximately three times more sensitive to the mAb than primed, CD45RA neg /R0 pos T cells. Notably, within the CD45RA pos subset, T cells with phenotypic evidence of prior activation, i.e., expressing Fas, were relatively insensitive to cM-T412, compared with Fas neg cells. Remarkably, while a decrease in the number of IL-4–producing T helper 2 (TH2)-type cells in the anti-CD4 treated group was observed, numbers of IFNg –producing T helper 1 (TH1)-type cells remained stable, resulting in a significant increase in the TH1/TH2 ratio. Our data show that treatment with depleting CD4 mAb does not eliminate the cells most strongly involved in the disease process, i.e., primed, IFNg –producing TH1-type cells, and may therefore give an explanation for the lack of beneficial clinical effects of depleting CD4 mAb in human chronic autoimmune disease. ( J. Clin. Invest. 1997. 99:2225–2231.)