The distribution of IgE plasma cells in lymphoid and non-lymphoid tissues of high-IgE responder rats: differential localization of antigen-specific and 'bystander' components of the IgE response to inhaled antigen.

Repeated exposure of high-IgE responder rats to antigen-containing aerosols stimulates IgE responses which last for several weeks, and are eventually terminated with the onset of immunological tolerance. Studies on the distribution of total and antigen-specific IgE plasma cells and IgE mRNA during antibody production, identified the lymph nodes draining the lower respiratory tract as the primary site for initiation of the IgE response to inhaled antigen; subsequently the response seeded to mucosa-associated lymph nodes but not to central lymphoid organs. A vigorous 'bystander' IgE response (approx. x 10 the specific response) was also observed, but this was restricted to areas directly draining sites of deposition of inhaled antigen, including non-lymphoid respiratory mucosal tissues. Despite the rapid termination of the specific IgE response after the fourth week of exposure, the bystander component persisted. These results are discussed in relation to the role of cognate/non-cognate T-B interactions in the IgE response to inhaled antigens, and the relative susceptibility of each component to T-cell regulation in vivo.