Studies of the immunological activities of the outer membrane protein from Escherichia coli.

The outer membrane protein (OMP) prepared from was found to be a potent mitogen for murine B cells and to be capable of inducing polyclonal antibody formation as well as a proliferative response. Spleen cells from nude mice responded equally as well to OMP as those from their normal litter-mates, whereas nylon-wool-purified T cells or thymocytes failed to respond. The proliferative response was dependent on the presence of macrophages. The macrophage dependency of the polyclonal antibody response seemed to be less than that of the proliferation. OMP was mitogenic for lipopolysaccharide (LPS)-resistant C3H/HeJ spleen cells, further indicating that OMP is an unique B-cell mitogen distinct from LPS. OMP also enhanced the specific antibody response sixty-seven-fold to an optimal dose of sheep red blood cells (SRBC) . The kinetics of the response, however, was not altered from that of cultures without OMP. The anti-SRBC response of spleen cells from C3H/HeJ mice was also enhanced by the addition of OMP, suggesting that the adjuvant effects were not due to the LPS in the preparation. Antibody responses to TI-1 antigens, trinitrophenyl-LPS (Boivin) (TNP-LPS) and TNP-, were not enhanced in the presence of OMP. In contrast OMP enhanced the response to TI-2 antigens, TNP-LPS (Westphal) and dinitrophenyl-Ficoll and T cells were shown to be required for these augmented antibody responses. Enhancement was not seen in nude mouse spleen cell cultures but was seen when nylon-wool-purified T cells were added to the cultures.