Induction of IgM immunological memory to lipoteichoic acids in rabbits. Part I.

Intravenous immunisation of rabbits with 10(9) lactobacillus fermentum cells elicited a response, specific for lipoteichoic acid (LTA), detectable as IgM plaque-forming cells (PFC) in the spleen by day 2 and as thiol-sensitive 19s antibodies in sera by day 3. Direct PFC responses peaked at day 6, with no indirect PFC demonstrable at the time. Specific IgG PFC appeared after 14 days. A second intravenous injection 5 weeks later induced a 10-fold higher IgM PFC response to LTA which reached a maximum on day 4. An enhanced specific IgG PFC response was also observed. Serum analysis showed further evidence of the anamnestic IgM response to LTA. The results are discussed in terms of the T-dependence of the LTA immunogen.