Self‐reactive T cells are activated by the 65‐kDa mycobacterial heat‐shock protein in neonatally thymectomized mice

To elucidate the mechanism of autoimmune disease in neonatally thymectomized (NTX) mice, we have investigated the responsiveness of the self‐reactive T cells which have not undergone clonal deletion in such animals. Consistent with a recent report (Yuuki et al., Eur. J. Immunol. 1990. 20: 1475), T cells bearing V_β11‐gene products capable of recognizing I‐E‐encoded molecules were readily detected in the mature T cell pool of NTX BALB/c (I‐E^d, Mls‐2^a) mice. The V_β11‐bearing T cells in NTX mice expressed interleukin 2 receptors and responded normally to signals delivered through the T cell receptor. Notably, these T cells in NTX mice proliferated significantly after culture with the 65‐kDa mycobacterial heat‐shock protein, whose amino acid sequence is highly homologous to that in eukaryotes. These results suggest that self‐reactive T cells in NTX mice may be activated by heat‐shock proteins derived from various pathogens and/or stressed autologous cells, resulting in the development of autoimmune diseases in such animals.