Aged rat macrophages exhibit ipaired response to in vitro stimulation with IL-4

The influence of aging on phagocytic, antigen presenting and secretory capacity of resident Albino Oxford rat peritoneal macrophages cultured for 24 hours in medium alone and in the presence of either LPS or IL-4 was examined. The frequencies of CD68+, CD169+ and CCR7+ cells were comparable among fresh peritoneal cells from young (3-months-old) and aged (i8-months-old) rats, whereas those of CD163+, MHCII+ and CD86+ cells were lower within the same cell population in aged relative to young rats. Congruent with the latter findings, aged rat macrophages cultured in medium alone exhibited impaired allostimulatory properties. Additionally, their zymosan phagocytizing ability was reduced. Differently from young rat macrophages, aged rat macrophages changed neither allostimulatory nor zymosan phagocytizing ability upon in vitro treatment with either LPS or IL-4. In the presence of LPS, NO production comparably increased in macrophages from young and aged rats. However, in the presence of either LPS or IL-4 urea production increased only in macrophages from aged rats. Differently from LPS, which increased the prototypic proinflamrnatory cytokine production in macrophages from rats of both ages, the diminishing effect of IL-4 on their production was evident only in macrophages from young rats. Collectively, our results suggest that aging, besides diminishing influence on macrophage allostimulatory and zymosan phagocytizing ability, may impair their responsiveness to IL-4 in vitro. Consequently, an altered efficacy of inflammatory/immune responses in aged rats may be expected.