HUMAN-LEUKOCYTE ANTIGEN CLASS-I IN POLYMYOSITIS - LEUKOCYTE INFILTRATES, REGENERATION, AND IMPULSE BLOCK

In polymyositis (PM), T-cell mediated myocytotoxicity is directed agai nst strongly human leukocyte antigen class I positive (HLA-I+) muscle fibers. Fiber regeneration probably is partly responsible for this HLA -I up-regulation. We have evaluated regeneration, denervation/impulse blockade, and focal leukocyte infiltrates as possible HLA-I inducing f actors in PM. Distinctive patterns of HLA-I, nerve cell adhesion molec ule (NCAM), and vimentin expression accompany denervation and regenera tion. Regenerating fibers also have centralized nuclei. Using semiquan titative methods, we examined strongly HLA-I+ fibers in PM muscle biop sies for these markers. Sarcoplasmic HLA-I levels were related to the presence of leukocyte infiltrates and invasion of fibers. Strongly HLA -I+ fibers were frequently invaded, and regeneration-associated change s were usually observed at sites of fiber damage. Sarcoplasmic HLA-I l evels were stable along intact fibers, also adjacent to leukocyte infi ltrates. A majority of the strongly HLA-I+ fibers were nonregenerating (NCAM(+) only). Though other mechanisms cannot be excluded, this sugg ests that impulse blockade or denervation may contribute to extra MLA- I up-regulation in these fibers. (C) 1997 John Wiley & Sons, Inc.