Methodological Considerations for Assessing Immune Defense in Reproductive Females

One of the key foci of ecoimmunology is understanding the physiological interactions between reproduction and immune defense. To assess an immune challenge, investigators typically measure an immune response at a predetermined time point that was selected to represent a peak response. These time points often are based on the immunological responses of nonreproductive males. Problematically, these peaks have been applied to studies quantifying immune responses of females during reproduction, despite the fact that nonreproductive males and reproductive females display fundamentally different patterns of energy expenditure. Previous work within pharmacological research has reported that the response to the commonly-used antigen keyhole limpet hemocyanin (KLH) varies among individuals and between females and males. In this heuristic analysis, we characterize antibody responses to KLH in females with varying reproductive demands (nonreproductive, lactating, concurrently lactating, and pregnant). Serum was taken from one animal per day per group and assessed for general and specific Immunoglobulins (Igs) G and M. We then used regression analysis to characterize the antibody response curves across groups. Our results demonstrate that the antibody response curve is asynchronous among females with varying maternal demands and temporally differs from the anticipated peak responses reflected in standardized protocols. These findings highlight the importance of multiple sampling points across treatment groups for a more integrative assessment of how reproductive demand alters antibody responses in females beyond a single measurement.