SPONTANEOUS LYTIC ACTIVITY AGAINST HETEROLOGOUS ERYTHROCYTES IN COTTON RAT (SIGMODON HISPIDUS) SERUM

Although innate immunity has been well studied in laboratory animal mo dels, no such documentation exists for wild species possessing a diver sity of physiological adaptations to their environment. We examined th e blood sera of 188 hispid cotton rats (Sigmodon hispidus) for natural ly occurring hemolytic activity against heterologous erythrocytes. Nin ety two percent of the blood sera samples from cotton rats lysed sheep erythrocytes. All sera tested against chicken erythrocytes showed hem olytic activity, while only 44% of the same sera could lyse bovine ery throcytes. No hemolytic activity was present in cotton rat sera agains t erythrocytes from other rodent species (Eastern woodrat, Neotoma flo ridana, and pine vole, Microtus pinetorum). Hemolytic activity was hea t labile and appeared to be mediated through the classical complement pathway. The protective nature of this hemolytic factor is unclear but it is probably directed at a more relevant molecule. These data, alon g with other reports of naturally occurring target specific serum fact ors in the cotton rat, may reflect the importance of innate protective mechanisms to small mammal populations.