In vitro temperature dependent activation of T-lymphocytes in Common wall lizards (Podarcis muralis) in response to PHA stimulation

Ecological immunology attempts to explain the variability of immune response among individuals by invoking costs and trade-offs, which may optimize the immune defence against pathogens. In ectotherms body temperature is correlated to that of the surrounding environment, so that their entire physiology, including immune functions, is influenced by the environmental temperature. We used in vitro phytohaemoagglutinin (PHA) stimulation in order to assess the effects of temperature on cell mediated adaptive response in male and female Common wall lizards (Podarcis muralis). Cell cultures were prepared from blood samples, inoculated with PHA and incubated at 22°C, 25°C, 32°C, and 38°C for three days. PHA stimulation caused proliferation of T-lymphocytes, but the effect depended on the incubation temperature. Lymphocyte proliferation was significantly impaired at both 22°C and 38°C compared to 32°C, which represented the highest levels of activation. Furthermore, lymphocyte activation was more variable in males while females were less immune suppressed than males at low temperatures. Differences between sexes suggest a possible influence of steroid hormones.