Total Immunoglobulin G Variation Through the Phenological Cycle of Migrant and Resident Lesser Long-Nosed Bats (Leptonycteris yerbabuenae) in the Drylands of Mexico and Its Relationship With Bacterial Killing-Ability of Plasma.

Bats have unique immunological characteristics among vertebrates. Understanding how the immune system responds during the life cycle of bat populations is crucial for grasping how their defenses against infection vary during critical life events. We used the lesser long-nosed bat (Leptonycteris yerbabuenae) as a model to assess adaptive humoral immunity (total immunoglobulin G concentration, tIgG) at different periods during the year involving different ages, reproductive conditions and migratory habits (females migrate seasonally to give birth while males are resident). We also determined the relationship of tIgG with previously published values of plasma bacterial killing ability against Escherichia coli (BKA). tIgG did not vary among reproductive periods in males and females, although higher values were measured in non-reproductive males in 2019 than in 2020. In contrast, tIgG was lower in young individuals than in non-reproductive and lactating females. The tIgG had a positive relationship with BKA in non-reproductive females, but no relationship was observed in non-reproductive males and reproductive females. These results suggest that tIgG is resilient to physiological and ecological changes experienced by adults throughout their reproductive and migratory cycle. The low tIgG during early life suggests that young individuals have not developed an IgG pool comparable to that of adults. The positive relationship between tIgG and BKA in non-reproductive females suggests that E. coli clearance is enhanced by the presence of antibodies that facilitate its elimination.