Quantification of absolute IgG concentration in bat sera

Abstract Bats are endowed with a remarkable capacity to withstand important pathogens through evolutionary adaptations in their immune systems. Antibodies are essential component of the adaptive immune response and serve as a crucial biomarker, indicating both present and past pathogen infections, as well as the overall physiological state of the organism. The main type of antibody found in the blood of mammals is IgG. It is produced as a result of specific T-cell-dependent antibody responses. Consequently, monitoring IgG in wild animals can yield valuable insights into pathogen dynamics and host responses. Currently, there is no simple technique for measuring absolute IgG concentration that can be generalized for different species of bats. The present study proposes a methodology to quantify total IgG levels in bats. The approach is based on an immunosorbent assay and employs only protein G as a detecting reagent for IgG. This method has the potential to be applied to diverse bat species, as well as other mammals. As a proof of concept, we present a detailed procedure to quantify serum IgG in Egyptian fruit bats ( Rousettus aegyptiacus ). The estimated concentration of IgG was found to be relatively high (5-6 mg/ml), highlighting the role of specific antibody responses in the immune defence of bats. To validate the method, we compare the results to an alternative approach based on SPR biosensor technology. Furthermore, data pertaining to the estimation of IgG levels in a different bat species, namely Myotis myotis , is presented. This simple and effective technique offers a valuable tool for advancing our understanding of immune function in bats and potentially other wild mammals, contributing to broader efforts in wildlife immunology and disease ecology.