Arthritis in mice: allogeneic pregnancy protects more than syngeneic by attenuating cellular immune response.

Objective: We tested the hypothesis that collagen induced arthritis benefits more from allogeneic pregnancy than syngeneic pregnancy.
Methods: Arthritis was induced in female B10.RIII (H-2r) mice by injecting bovine type II collagen. Female mice were subsequently paired, one group with q-haplotype males (B10.Q) and the other with r-haplotype males (B10.RIII). The effect of q- and r-haplotype was measured by determining the acute phase reactant serum amyloid A (m-SAA), bovine anti-collagen type II antibodies (a-CBII), and the ratio of CD4/CD8 T lymphocytes during pregnancy and after delivery. Clinical assessment of arthritis was also performed.
Results: The number of mice with maximum severity of clinical arthritis was significantly higher in the syngeneic group (11/20 vs 5/21; p = 0.04). Although we noted that in the allogeneic group the females had had a significantly higher level of a-CBII during pregnancy (p = 0.02), we also found that the ratio of CD4/CD8 was higher in the syngeneic group even if it was measured during (p = 0.04) or after gestation (p = 0.05). Taking into account all the cases of arthritis initiated in the post-gestational period there was no difference in m-SAA or in a-CBII between the 2 groups, but the ratio of CD4/CD8 was higher in the syngeneic group measured during (p = 0.03) or post gestation (p = 0.02).
Conclusion: Allogeneic pregnancy benefits more than syngeneic pregnancy by attenuating the cellular immune response, and the ratio of CD4/CD8 indicates the attenuation of cellular immunity when measured during gestation or post partum.