Comparative humoral responses to Escherichia coli and sheep red blood cell antigens introduced via the respiratory tract.

The numbers of specific antibody-forming cells (AFC) in mediastinal lymph nodes (MLN) and spleen were determined in Balb/cByJ mice following inhalation or intratracheal (IT) injection of acetone-dried E. coli or its lipopolysaccharide (LPS). These responses were compared with those obtained using sheep red blood cells (SRBC), an antigen previously used in studies of pulmonary immunity. Inhalation of aerosolized E. coli for as little as 2 min produced significant numbers of AFC in both MLN and spleen, while equivalent administrations of SRBC produced few AFC at either site. Similarly, IT instillations of E. coli resulted in recovery of AFC from MLN and spleen, while IT SRBC produced AFC in MLN but few splenic AFC. IT installations of radiolabeled SRBC and E. coli were used to examine antigen dissemination, and no differences were found in the amounts of radiolabel recovered from various tissues following instillation of either antigen. Experiments using endotoxin resistant mice, and using administrations of LPS in combination with SRBC, were unable to demonstrate alterations in AFC production due to effects of LPS. It was found, however, that inhaled or IT injected E. coli or LPS produced greater pulmonary inflammation than did similar administrations of SRBC, and this may be at least partly responsible for the enhanced induction of systemic immunization.