Absence of CD43 fails to alter T cell development and responsiveness.

Genetic elimination of CD43 has been associated with increased T cell adhesiveness and T cell hyperresponsiveness to mitogens and alloantigens. Therefore, we investigated whether T cell development was perturbed in CD43-deficient mice by breeding CD43(null) mice with male Ag (Hy)-specific TCR-transgenic mice. Neither positive nor negative thymic selection of male Ag-specific T cells were affected by CD43 status. Furthermore, we did not observe a substantial or consistent hyperresponsive pattern in HY-CD43(null) lymph node cells compared with littermate HY-CD43(+/-) lymph node cells upon analysis of in vitro T cell stimulation with male Ag or mitogen. These observations challenged original conclusions associating absence of CD43 with T cell hyperresponsiveness and led us to re-examine this association. Reported phenotypes of CD43(null) mice have been based on mice with a mixed 129xC57BL/6 genetic background. To exclude a possible influence of genetic background differences among individual mice we analyzed CD43(null) littermates that had been back-bred onto the C57BL/6 background for seven to eight generations. We found that CD43(+) and CD43(null) littermates with the C57BL/6 background exhibited no differences in response to mitogen or alloantigen, thereby establishing that T cell hyperresponsiveness is not a general correlate of CD43 absence.