Cell-mediated immunity in poultry

Abstract

In avian species, adaptive immunity involves both humoral and cell-mediated immune (CMI) responses. Although humoral or antibody-mediated immune responses are particularly effective against extracellular antigens, CMI responses are specialized in the elimination of intracellular antigens; the latter include those that have entered cells via the endocytic pathway (exogenous antigens; e.g., phagocytosed bacteria) or were produced within the cell such as viral proteins and proteins resulting from neoplastic transformation of the cell (endogenous antigens). CMI responses, like most humoral immune responses, are tightly regulated and require "help" from T helper cells, specifically the type 1 T helper cells (Th1, hence, the name Th1 responses). Th1 cells are characterized by their production of cytokines such as interferon-gamma (IFN-gamma), tumor-necrosis factor-alpha (TNF-alpha), and interleukin-2 that drive CMI responses. The functional effectors of CMI responses are various immune cells including cytotoxic lymphocytes (cytotoxic T cells and natural killer cells) and macrophages. Cytotoxic lymphocytes and macrophages are specialized in the elimination of endogenous and exogenous antigens, respectively. In the past decade, substantial progress has been made in defining the role and regulation of avian CMI responses. Other advances have addressed strategies that strengthen this arm of adaptive immunity to optimize defense as well as protection against neoplastic diseases and nonneoplastic diseases caused by intracellular pathogens.

Differential antimicrobial peptide gene expression patterns during early chicken embryological development

“…As a result, it is now known that the immune system in poultry, like that of mammals, has developed several defence strategies to cope with a wide spectrum of pathogens [33,34] . Despite the multiple immunodefensive mechanisms present in eggs -AMPs in eggshell [35] , iron depleted and lysozyme-rich egg white, and antibodies in yolk [3,36,37] , eggs do become contaminated during oviposition in the reproductive tract of the hen or from external bacteria that cross the shell [17,18] .…”

Resilience in farm animals: biology, management, breeding and implications for animal welfare

“…T H 1 cells secrete Type I cytokines, including interferon-g and interleukin-12, which largely promote cell-mediated immune responses whereas T H 2 cells produce Type II cytokines, including IL-4 and IL-5, which largely promote antibody-mediated immune responses. The existence of a similar T H 1/T H 2 paradigm has been investigated in several farm animal species including chickens (Vandaveer et al 2001;Erf 2004), pigs (Schmied et al 2012); (Raymond and Wilkie 2004) and cattle ). Although polarised cell-mediated and antibody-mediated responses to intracellular and extracellular pathogens respectively are observed in these production animals, evidence suggests that the T H 1/T H 2 paradigm established in mice is an oversimplification of a more complex immunoregulatory framework operating in these species .…”

Evolution of the polymorphism at molecular markers in QTL and non-QTL regions in selected chicken lines (Open Access publication)

“…However, as in mammals, immune responses in avian species are specialised in the elimination of antigens: responses to antigens are Th1-or Th2-mediated [7]. Th1 responses require the interference of type 1 T helper cells that directs immune response toward a cell-mediated response (cellular pathway).…”