THE HETEROGENEITY OF THE AGE-RELATED DECLINE IN IMMUNE-RESPONSE - IMPAIRMENT IN DELAYED-TYPE HYPERSENSITIVITY AND CYTOTOXIC LYMPHOCYTE-T ACTIVITY OCCUR INDEPENDENTLY

Aged mice are known to have a heterogeneous cytotoxic T-lymphocyte (CTL)response to an influenza challenge. We sought to determine whether delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) was also heterogeneous in aging and, if so, whether this correlated with anti-influenza CTL activity. Aged mice developed mean footpad swelling of 0.24 +/- 0.09 mm following SRBC challenge and mean CTL activity of 35 +/- 18%. Even though these values were significantly lower than those from young mice (0.54 +/- 0.10 mm and 51 +/- 2%, respectively), no correlation was found between anti-influenza CTL activity and DTH to SRBC (r = 0.0 1). We believe the most likely reason for this independent decline in immune response is because different activation signals are required for DTH and CTL activity. Our data thus suggest an age-related functional mosaicism in the immune system.