VARIABILITY OF IMMUNE-RESPONSE TO HETEROLOGOUS ERYTHROCYTES DURING POPULATION-CYCLES OF RED (CLETHRIONOMYS RUTILUS) AND BANK (C-GLAREOLUS) VOLES

Immunocompetence is regarded to be one of the principal links in mecha nisms of population regulation in small mammals. We assessed immune re sponsiveness to injection of sheep red blood cells (SRBC) in sympatric populations of red and bank voles in southern West Siberia, Russia, d uring the cycle of density from 1991 to 1995. We used a splenic plaque -forming cells (PFC) technique to measure the immune response to the a ntigen. In an attempt to establish relationships of immunity with intr insic factors involved in population regulation we monitored the follo wing parameters: population numbers, recruitment rate, and adrenocorti cal activity. The analysis of covariance showed a significant effect o f reproductive status of voles and independent significant effects of month and year of capture on immune response to SRBC. In general, imma ture young was significantly higher responders as compared to mature ( breeding) adults. The seasonal and long-term variations in numbers of PFC were similar in both species. Seasonal minimum of the immune respo nse was observed within the period of intensive breeding in June and J uly. Among the years the immune responsiveness was maximal in the phas e of population depression. The increase in maturation rate as density increased coincided with a decrease in immune responsiveness. The cor relation analysis showed little or no evidence of links between the im munity and adrenocortical activity in the populations under study. Bas ed on the patterns of seasonal and long-term variations of surveyed va riables it is likely that physiological mechanisms governing the proce sses of sexual maturation and reproduction of red and bank voles are i nvolved in the regulation of immunity.