Effect of pregnancy on collagen-induced arthritis in mice.

Bovine type II collagen administered to non-pregnant female DBA/1 mice caused arthritis in 55% of animals with a mean onset time of 70 days following immunization. Of collagen-treated females subsequently becoming syngeneically pregnant before the onset of arthritis, all developed the disease within 10 days of parturition, representing an earlier onset, compared to non-pregnant females, of 41 days. This earlier onset also occurred in females with an allogenic pregnancy, but did not occur in females resorbing their fetuses (only syngeneic pregnancies were examined). In females with arthritis at the time of conception a significant remission was observed during pregnancy followed by exacerbation post-partum. This sequence of remissions during pregnancy and exacerbations post-partum occurred with each pregnancy (parties of up to four studied). The treatment of multiparous females with collagen demonstrated that pregnancy does not provide long-term protection against the development or progression of arthritis, as such females were equally susceptible to post-partum onset of collagen-induced arthritis (CIA) and the remissions and exacerbations described above. The modifying effect of pregnancy on CIA in mice is complex and does not appear to be the result of a single pregnancy-associated phenomenon.