种群内部因素对动物免疫功能的影响

Effects of Intra-populational Factors on Immunocompetence of Animals

动物的免疫状况与种群动态的关系是近年来动物生态学研究的热点之一。总结了种群内部因素对动物免疫功能的影响 ,并介绍了几种免疫调节假说。对于不同的研究对象 ,种群密度的高低对其可产生不同的影响。在一个种群中 ,优势个体往往具有较高的免疫水平 ;雌性个体的免疫水平高于雄性个体 ,这可部分归因于性激素的作用。动物处于繁殖期时免疫水平有所下降。婚配制度的作用效果是复杂的 ,为了能够成功进行繁殖而面临更大选择压力的性别可能具有更强的免疫功能。许多研究者根据野外研究结果探讨了种群调节的免疫机制问题 ,认为个体的免疫能力受到遗传和环境因素的影响 ,其变化状况将关系到整个种群的数量波动。还介绍了生态学研究中采用的免疫学指标 ,评价了这些指标对实验结果的影响 ,并对今后的研究方向提出了几点建议。

The relationship between immunocompetence and population dynamics has been received much attention by animal ecologists recent years. The effects of intra\|populational factors on the immunocom\| petence were reviewed and some immunoregulation hypotheses were introduced. Population density and sociality are important factors to affect immune functions. Single living and low population density can suppress the immunocompetence for highly sociality species. However, the rapid changes in environmental conditions and population densities also can cause the modifications in immune functions. Social hierarchy can influence the immunocompetence, too. Within a population, dominant individuals usually have higher immune responses than the others. However, the subdominants and submissive individuals show different behaviors and different immune responses. The intensity, duration and frequency of the social conflict are close related to the immune functions. Sex and hormones are also important factors responsible for immunocompetence. Generally female individuals have higher immune responses than males and this was thought that mainly because of the functions of sexual hormones. Estrogen can enhance the humoral immunity but suppress the cell\|mediated immunity. Androgen can suppress both sides of acquired immunity. Some immunosuppression hypotheses (such as resource allocation hypothesis, immunocompetence handicap hypothesis, and immunoredistri\| bution hypothesis) are proposed based on the functions of sexual hormones. Reproductive effort can suppress the immunocompetence, therefore, animals usually have lower immune responses during reproductive period. The effect of mating system on immunocompetence is complex. Those male and females that face greater selection pressure for reproductive success may have higher immune responses. Animal's immune functions can influence the population dynamics. Within a population, individual's immunocompetence can be affected by both genetic and environmental factors, and the changes in capacity of immune responses can be related to the population fluctuation. To choose the immunological indices and their effects on the experimental results are evaluated. Some suggestions for the future research in this field are proposed.