C4, BF, C3 allele distribution and complement activity in healthy aged people and centenarians.

The aim of this study was to examine the complement system and the distribution of some human leukocyte antigen (HLA) class III alleles (C4, BF) in healthy aged people (77 centenarians and 89 elderly subjects). We have also studied the alleles of C3, a complement component genetically unrelated to HLA, the immunochemical levels of C4 and C3 and serum functional hemolytic activity for classical (CH50) and alternative (AP50) complement pathway. The levels of C3 and C4 and the CH50 and AP50 were found to be within the normal range. The frequencies of C3, BF, and C4A alleles were similar in the cohorts that have been studied. For C4B null allele (C4BQ0) a trend toward an increase in the older cohort was observed, although the differences were not significant after statistical correction. Our data suggest that the complement system is well preserved in centenarians and elderly subjects and class III HLA antigens are equally distributed in aged cohorts and in young healthy individuals.