ANTIBODY-RESPONSE TO PNEUMOCOCCAL POLYSACCHARIDE VACCINE IN YOUNG, ADULT AND OLD MICE

The anti-pneumococcal antibody response was studied in young (5-week-o ld) and adult (10-week-old) BALB/c and CBA/J mice and in adult (9-10-w eek-old) and old (12-, 18- and 24-month-old) AB6F1 and B6D2F1 mice aft er s.c. immunization with a 23-valent pneumococcal polysaccharide vacc ine. Both young and adult mice showed a significant IgM antibody respo nse to the vaccine 6 days after immunization with 1-11 mug antigen. Th ere were significant immune responses to serotypes 1, 2, 4 and 7F in c ontrast to small responses to serotypes 14, 19F and 23F after immuniza tion with the vaccine. One month after immunization, there were only m arginal differences in IgM anti-pneumococcal antibody levels to the va ccine (anti-PPS) between immunized and unimmunized BALB/c mice, wherea s in CBA/J mice the anti-PPS remained higher in immunized than in unim munized mice. Immunization of old mice induced a significant IgM antib ody response 6 days after immunization, but the anti-PPS thereafter de creased rapidly towards preimmunization values in AB6F1 mice. A signif icant IgG anti-PPS was not detected in any of the mice studied. The Ig A anti-PPS tended to vary over time with no consistent pattern. It is important to carefully consider age and strain of the mice used when s tudying the immune response to pneumococcal polysaccharide antigens.