Abstract
Reptiles represent the crucial phylogenetic group as they were the ancestors of both birds and mammals hence very important to study. The objectives of the present study were to investigate the potential roles of testosterone in the innate immune responses and splenic lymphocyte proliferation in fresh water snake, Natrix piscator. Animals were mildly anesthetized and spleens were taken out to study the splenic macrophage phagocytosis, super oxide production and nitrite release using in vitro testosterone. Splenic lymphocytes were isolated by density gradient centrifugation and were studied for mitogen induced proliferation in presence of in vitro testosterone. Testosterone suppressed the phagocytosis and nitrite release in a concentration dependent manner. Biphasic suppressive effect of testosterone was observed in superoxide production as judged by reduction of nitroblue tetrazolium salt where salt reduction was suppressed at lower and higher concentrations of testosterone. Mitogen induced splenic lymphocyte proliferation was also suppressed by testosterone. By suppressing immune responses, testosterone may, therefore, act as a physiological mechanism regulating the relative amount of energy invested into either reproductive effort or immunocompetence.
Highlights
The immune system is a coordinated unit consisting of variety of cellular and humoral components that responds to foreign pathogens/factors, with the goal being to eliminate them and return to steady state that existed prior to detection of the same
As sexual dimorphism is evident, only males were used in this study during April and May, when animals were reproductively inactive [33]
In the present investigation on cellular immune responses, we found that the percentage phagocytosis was significantly decreased, when splenic macrophages were treated with testosterone, but no change occurred in the phagocytic index
Summary
The immune system is a coordinated unit consisting of variety of cellular and humoral components that responds to foreign pathogens/factors, with the goal being to eliminate them and return to steady state that existed prior to detection of the same. Field studies in mammals and birds have illustrated that the prevalence (i.e. proportions of the individual infected) and intensity (i.e. severity of the infection) of parasitic infections are often higher in male than female [7,8]. Males generally exhibit lower immune responses than the female conspecifics [2,8]. The humoral immune responses (i.e., antibody production by B-cells) are typically elevated in females, as compared with males. Females of various species display higher IgM, IgG and IgA concentrations than males and are better able to mount both primary and secondary antibody response to antigenic challenge than males [1,14,15]
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