Specific intracellular adhesion molecule-grabbing nonintegrin R1 is not involved in the murine antibody response to pneumococcal polysaccharides.

Streptococcus pneumoniae is a microorganism that frequently causes serious infections in children, the elderly, and immunocompromised patients. We studied whether the specific intracellular adhesion molecule-grabbing nonintegrin R1 (Sign-R1) receptor, involved in the uptake of capsular polysaccharides (caps-PS) by antigen-presenting cells, is necessary for the antibody response to pneumococcal caps-PS and phosphorylcholine (PC). The antibody response to caps-PS and PC was evaluated after vaccination with soluble caps-PS (Pneumovax) and after vaccination with heat-killed S. pneumoniae. The role of Sign-R1 was investigated by using Sign-R1 knockout mice and anti-Sign-R1 monoclonal antibodies. The immunoglobulin M (IgM) and IgG antibody response to PC and caps-PS (serotypes 3 and 14) was not affected by anti-Sign-R1 monoclonal antibodies. The IgM antibody response in Sign-R1 knockout mice was comparable to the antibody response in wild-type mice. The IgG antibody response to serotype 3, but not to serotype 14, tended to be lower in Sign-R1 knockout mice compared to wild-type mice. In conclusion, we found that Sign-R1 is not involved in the IgM antibody production to PC and caps-PS serotype 3 or 14 and the IgG immune response to PC and caps-PS serotype 14. There is no direct relation between capture and uptake of caps-PS serotype 14 by Sign-R1 and the initiation of the anti-caps-PS antibody production in mice.