Post‐thymectomy autoimmune gastritis: fine specificity and pathogenicity of anti‐H/K ATPase‐ reactive T cells

Thymectomy at day 3 of life (d3Tx) results in the development of organ‐specific autoimmunity. We have recently shown that d3Tx BALB/c mice which develop autoimmune gastritis contain CD4+ T cells specific for the gastric parietal cell proton pump, H/K ATPase. Here, we demonstrate that freshly explanted gastric lymph node (LN) cells from d3Tx mice react significantly to the H/K ATPase α chain, but only marginally to the β chain. Two H/K ATPase‐reactive T cell lines were derived from the gastric LN of d3Tx mice. Both are CD4+ , TCR α / β+ , and I‐Ad restricted, and recognize distinct peptides from the H/K ATPase α chain. One cell line secretes Th1 and the other Th2 cytokines, but both are equally potent in inducing gastritis with distinct profiles of cellular infiltration in nu/nu recipient animals. Neither of the cell lines induced disease in normal BALB/c recipients and transfer of disease to nu/nu recipients was blocked by co‐transfer of normal BALB/c spleen cells containing CD4+ CD25+ cells. Although CD4+ CD25+ T cells are thought to emigrate from the thymus after day 3 of life, they could be identified in LN of 2‐day‐old animals. The capacity of CD4+ CD25+ T cells to abrogate the pathogenic activity in vivo of both activated Th1/Th2 lines strongly suggests that this suppressor T cell population may have a therapeutic role in other models of established autoimmunity. The availability of well‐characterized lines of autoantigen‐specific T cells should greatly facilitate the analysis of the mechanism of action and target of the CD4+ CD25+ immunoregulatory cells.