EVIDENCE FOR GENETIC-BASIS OF SEASONAL DIFFERENCES IN ANTIBODY-FORMATION BETWEEN 2 MOUSE STRAINS

In order to confirm the presence of an acrophase difference based upon genotype in the seasonal expression of an immune competence end point , splenic plaque-forming cell (PFC) response to sheep red blood cells (SRBC), female B6C3F1 and CD1 mice were concurrently studied for PFC r esponse during two studies performed in each season for 1 year. Mice w ere multiply housed, fed ad libitum, and standardized to light (06:00- 18:00); dark (18:00-06:00). For each strain and study, subgroups were either naive (n = 10), received a vehicle (n = 10) or Cytoxan (n = 5). Challenge with SRBC occurred in early afternoon 4 days before harvest ing of spleens and PFC assay. All other procedures were performed earl y in the daily light span. Analysis of variance and single cosinor ana lysis revealed a significant seasonal time effect for PFC in naive mic e of both strains. Antibody formation was greatest in spring for CD1 m ice and in summer for the B6C3F1 mice. These acrophases were consisten t with earlier results for both strains and show the phenomena to be r eproducible and genetically based.