ІМУННА СИСТЕМА ПТИЦІ ТА ССАВЦІВ: ПОРІВНЯЛЬНА ХАРАКТЕРИСТИКА

Abstract

Огляд присвячений висвітленню спільних та відмінних морфологічних та функціональних особливостей імунної системи двох класів тварин – ссавців та птиці. Розглянуто відмінності первинних та вторинних імунних органів птиці, особливості імунокомпетентних клітин та основних молекул імунної системи. Розкрито важливість подальшого вивчення імунної системи птиці з точки зору фундаментальної імунології та для розуміння фізіології імунних механізмів при селекції, профілактиці та лікуванні птиці.

This review summarises the current state of knowledge of the chicken's immune response, highlighting differences in the bird compared to mammals. Birds and mammals evolved from a common reptilian-like ancestor over 200 million years ago, so there has been ample opportunity for parallel evolution in the development of their immune systems. The avian immune system operates on the same general principles as the mammalian immune system. Antigenic stimulation initiates an immune response that involves cellular cooperation most notably between macrophages, B lymphocytes and T lymphocytes. Macrophages process the antigen and present the antigen to the lymphocytes. B lymphocytes, the principal cells that mediate humoral immunity, transform into plasma cells and produce antibodies. T lymphocytes, most important for cellular immunity, differentiate into functionally diverse subpopulations. Among the avian species, the immune system of the chicken has been studied most extensively. There are many similarities between the general immune mechanisms of mammals and chickens. There are also important differences. Our knowledge of the avian immune system and the avian immune response to disease and vaccination still lags behind that of better studied biomedical model systems, such as the human and mouse, progress has been dramatic. Thanks to the chicken genome sequence, we now have far greater understanding of the genes and molecules available to the avian immune response and, therefore, access to the tools required to enable us to understand the biology of that response in far greater detail than previously. In broad terms, the immune systems and responses of mammals and birds are similar. However, when one looks at the organs, cells, and molecules of the immune response in birds, one begins to understand that mammals and birds achieve the same overall responses often in quite different ways and, in many respects (but not all), the avian immune response is different. Birds rely on gene conversion to generate an antibody repertoire, and the major histocompatability complex is some 20-fold smaller than that of mammals. Birds respond to antigenic stimulation by generating antibodies as well as cellular immunity. There are three principal classes of antibodies in birds i.e., IgM, IgG (also called IgY) and IgA. Antibody diversity is achieved by gene conversion. T cells are the main effector cells of cellular immunity. Recently, genes of several avian cytokines have been cloned and expressed. In order to develop novel solutions to avian disease problems, including novel vaccines and/or vaccine adjuvants, and the identification of disease resistance genes which can feed into conventional breeding programmes, it is necessary to gain a more thorough understanding of the avian immune response and how pathogens can subvert that response. Studies of avian vaccinology provide important insights as well as pioneering developments, such as embryonic vaccination. Avian immunology is a growing field of study that offers exciting prospects and still has much to contribute to mainstream immunology.