Expansion of intermediate T cell receptor cells expressing interleukin-2 receptor alpha(-) beta(+), CD8 alpha(+) beta(+), and lymphocyte function-associated antigen-1(+) in the liver in association with intrahepatic islet xenograft rejection from rat to mouse - Prevention of rejection with anti-interleukin-2 receptor beta monoclonal antibody treatment

Background. The precise mechanisms involved in islet xenograft rejection remain unknown. The purpose of the present study was to determine cellular mechanisms responsible for islet xenograft rejection in the liver to facilitate finding a procedure for prevention of immune rejection. Methods. Hepatic mononuclear cells (MNC) as well as splenocytes, peripheral blood MNC, and thymocytes from streptozotocin-induced diabetic mice (BALB/c) rejecting the intrahepatic rat (Lewis) islet xenografts were isolated and examined by two-color FAGS analysis. Results. The characteristic finding of the hepatic MNC from the mice rejecting islet xenografts compared with mice receiving isografts was a significant increase in the yield as well as in the percentage of the cells expressing CD3(+) interleukin-2 receptor (IL-2R) alpha(-)beta(+), CD3+ CD8 alpha(+)beta(+), and T cell receptor (TCR) alpha beta(+) lymphocyte function-associated antigen-1(+). The expression of CD3 and TCR alpha beta of these T cells was found to be of intermediate intensity (TCRint cells). The expansion of these TCRint cells occurred predominantly in the liver. There was no significant difference in the cells expressing CD3(+) IL-2R alpha(+), CD3(+) CD4(+), CD3(+) TCR gamma delta(+), CD3(-) IL-2R beta(+) (natural killer cells), and B220(+) (B cells). In vivo administration of anti-IL-2R beta monoclonal antibody directed to the expanded cells produced a prevention of rejection. Conclusions. These findings suggest that islet xenograft rejection in the liver from rat to mouse is an event for which the TCRint cells are responsible.