B Cell Memory to Thymus-independent Antigens Type 1 and Type 2: the Role of Lipopolysaccharide in B Memory Induction

Several studies have indicated that thymus-independent (TI) antigens, unlike their thymus-dependent (TD) counterparts, are poor at generating memory antibody responses (Immunol. Today 1981. 3:217). In contrast to this view, the present report shows that the TI type 1 (TI-1) antigen, 2,4,6-trinitrophenyl-lipopolysaccharide (TNP-LPS), elicits good secondary responses in rats. These secondary antibody responses are not only greater in magnitude than the primary responses, but display a different pattern of Ig classes with more IgG and IgA antibodies produced. In transfer experiments between congenic strains of rats which differ in their kappa light chain Ig allotype, it is shown that this memory is attributable to persistent B cell clones. The TI-2 antigen, 2,4-dinitrophenyl-hydroxyethyl starch (DNP-HES), given alone did not elicit B cell memory. However, when DNP-HES is presented to the immune system in association with LPS, the pattern of the anti-DNP response is similar to that elicited by TNP-LPS. The capacity to generate TI memory is associated with the appearance of hapten-specific B cells in the marginal zones of the spleen. Hapten-binding cells were induced in the marginal zones following immunization with TNP-LPS, but not by DNP-HES. However, concurrent immunization with DNP-HES and LPS which were not covalently linked was found to induce DNP-binding cells in the marginal zone. There is complete correlation between the appearance of hapten-binding memory B cells in the marginal zone and the capacity of these antigens to induce secondary responses.