Age‐Dependence of the IgA Anti‐α(1→3) Dextran B1355 Response in Vitro

The magnitude of the Balb/c mouse IgA anti-alpha (1 leads to 3) dextran B1355 (anti-dex) response in vivo was recently found to be markedly T-cell-dependent and age-dependent. This report demonstrates that the in vitro IgA anti-dex response by mesenteric lymph nodes (MLN) is highly age-dependent and that there is an age-dependent increase of the background IgA anti-dex plaque-forming cell (PFC) response occurring in the absence of added antigen which correlates significantly with the magnitude of the antigen-stimulated response. In aging mice both background and antigen-stimulated IgA anti-dex responses appeared to be significantly higher in MLN than in spleen cultures. Moreover, it is shown that there is a striking increase with age of natural antibody in the serum of normal Balb/c to alpha (1 leads to 3) glucan determinants, particularly IgA and lesser amounts of IgM and IgG3.