INCREASED GRANZYME-B MESSENGER-RNA AFTER ALLOINCOMPATIBLE MYOBLAST TRANSPLANTATION

Normal C57BL/10SnJ myoblasts were transplanted into the tibialis anter ior of C57BL/10SnJ, C57BL/ScSn mdx; or BALB/c mice, These transplantat ions allowed us to investigate the immunoresponse not only against MHC but also against dystrophin introduced in the dystrophic muscles by s uch transplantations. Recently, our group reported following myoblast transplantations cellular infiltration of the host muscle by class II MHC cells, macrophages, and lymphocytes expressing CD4 or CD8 and IL-2 receptors. In the present study, activation of these infiltrating lym phocytes was investigated by measuring the expression of granzyme B mR NA. We used reverse-transcriptase polymerase chain reaction to detect granzyme B mRNA at various intervals after myoblast transplantations. To standardize the results, the mRNA were reverse transcribed using an oligo (dt) so that beta-actin mRNA could also be amplified from the s ame cDNA preparation. Granzyme B mRNA was increased for at least 3 wee ks after MHC alloincompatible grafts. The absence of increased granzym e B expression after allocompatible transplantation in mdx mice sugges ts that dystrophin is not sufficiently immunogenic to induce short ter m acute rejection, These results indicate that lymphocytes infiltrated in muscles injected with histoincompatible myoblasts are activated an d sustain the requirement for an adequate immunosuppression after such transplantations.