SERUM ANTIBODY-RESPONSES BY MALE AND FEMALE C57B1 6 MICE INFECTED WITH GIARDIA-MURIS/

We compared the levels of serum antibodies in male and female C57B1/6 mice during the primary and after challenge infection with Giardia mur is. Male mice began passing cysts in their faeces earlier than females , and were shedding cysts for over 60 days, while females stopped shed ding cysts by day 20 after infection. In both males and females there were significant increases in parasite-specific IgM 10 and 20 days aft er infection. No differences in parasite-specific serum IgA. were obse rved until 40 days after infection. Parasite-specific IgG (whole) leve ls were elevated on days 20 and 40 in females, while males showed no s ignificant increases. In addition, females had a much stronger IgG2b a nd IgG3 response than males. After challenge with either cysts or solu ble parasite protein only the females had significant increases in spe cific anti-parasite IgG2b. Our data show differential ability of males and females to control the infection with G. muris is paralleled by a difference in the anti-parasite serum IgG response of the mice.