Decreased in vitro lymphocyte stimulation and reduced sensitivity to IL-2 in patients with alopecia areata.

: The response to the T-cell growth factor interleukin-2 (IL-2) and to phytohemagglutinin (PHA) and concanavalin A (Con-A) were investigated in 63 patients with alopecia areata (AA) and in control subjects. The proliferative response to mitogens and to IL-2 determined by measuring [3H]-thymidine incorporation 72 h after stimulation is generally decreased in AA patients. The response to mitogens and to IL-2 was related to the response to the topical sensitizer SADBE (squaric acid dibutylester) and patients with no allergic reaction to this substance showed a marked reduction in lymphocyte stimulation, especially with IL-2. HLA typing of 34 of the 63 AA patients was performed in order to investigate the immunogenetic basis of hyporesponsiveness to topical sensitization. The relationship between reduced in vitro response to mitogens and particularly to IL-2, and in vivo response to sensitization to SADBE and the presence of HLA-DR5 are discussed.