Regional dichotomy of idiotypic expression on senescent B lymphocytes in systemic and mucosal immune systems: selective changes in NPb and T15 idiotypes with aging.

The age-associated changes in the expression of NPb and T15 idiotypes on antibody-secreting B cells in the spleen and bronchial lymph nodes (BLN) of mice following peritoneal immunization with (4-hydroxy-3-nitrophenylacetyl) acetic acid (NP) and phosphorylcholine (PC) as antigens were investigated. Changes in the NPb or T15 idiotype expressions were detected by the inhibition of anti-NP or anti-PC elispot-forming cells (SFC) with monoclonal (Mab) anti-idiotypic antibodies, Mabs Ac38 and Ac146, or AB1-2, respectively. We found that Mabs Ac38 and Ac146 significantly inhibited anti-NP IgM and IgG SFC responses in the spleen from 4-month old animals in a dose-dependent manner as opposed to a lack of effect on 24-month old splenic cells. There were no significant effects on anti-NP SFC responses in the BLN from either young or old mice. Similar results were obtained using Mab AB1-2 inhibition of T15 idiotype on anti-PC SFC responses in the spleen and BLN. No age-related changes in the gamma- and kappa-light chain contents of the secreted anti-NP antibodies by B cells in the spleen and BLN were observed. The kinetics of the appearance of endogenously auto-anti-idiotype blocked, hapten augmentable (HA) anti-NP IgM SFC responses revealed significantly higher percentages of HA SFC in the spleen and BLN, 14 days after immunization for both young and old mice. The findings suggest that the age-related changes in the idiotypic expression on antigen-specific antibody repertoires in the spleen and mucosa-associated tissues may be caused by the activation of subsets of B cells with different VH gene expressions.