Heterogeneity in the immune response to serotype b LPS of Actinobacillus actinomycetemcomitans in inbred strains of mice

We investigated the heterogeneity of the humoral immune responses to whole cells and lipopolysaccharide (LPS) of Actinobacillus actinomycetemcomitans serotype b and production of cytokines in inbred strains of mice. Nine such strains were tested: A/J (H-2(a)), C57BL/6 (H-2(b)), BALB/c (H-2(d)), DBA/ 2 (H-2(d)), B10.BR (H-2(k)), C3H/He (H-2(k)), C3H/HeJ (H-2(k)), DBA/1 (H-2( q)) and B10.S (H-2(s)). Mice were immunized intraperitoneally with whole ce lls of A. actinomycetemcomitans ATCC 43718 (serotype b) in phosphate buffer ed saline (PBS; pH 7.2) emulsified with an equal volume of Freund's incompl ete adjuvant. Serum immunoglobulin G (IgG), immunoglobulin A (IgA) and immu noglobulin M (IgM) levels against A. actinomycetemcomitans were measured by an ELISA system. ELISA analysis, using LPS fractions from serotype a, b or c strains of A. actinomycetemcomitans as the coating antigens, revealed th at mice strains C3H/He, C3H/HeJ, B10.BR and B10.S had an extremely high-IgM response against serotype b LPS. High-IgM titer sera contain also elevated levels of IgA antibodies to the antigen. To compare the cytokine productio n among inbred mice, the amounts of interleukin-4 (IL-4), interleukin-5 (IL -5), and interleukin-6 (IL-6) released from mouse splenocytes were measured using ELISA systems specific for these cytokines. A. actinomycetemcomitans serotype b LPS stimulation induced IL-6 release from murine splenocytes of all tested strains. However, IL-4 and IL-5 were detected only in high-IgM/ IgA responders to A. actinomycetemcomitans serotype b LPS, not in low-IgM/I gA responders. Thus, we found a relationship between the humoral immune res ponse to LPS of A. actinomycetemcomitans serotype b and production of type 2 cytokines by splenocytes. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.