Integrins are large heterodimeric type 1 membrane proteins expressed in all nucleated mammalian cells. Eighteen α-chains and eight β-chains can combine to form 24 different integrins. They are cell adhesion proteins, which bind to a large variety of cellular and extracellular ligands. Integrins are required for cell migration, hemostasis, translocation of cells out from the blood stream and further movement into tissues, but also for the immune response and tissue morphogenesis. Importantly, integrins are not usually active as such, but need activation to become adhesive. Integrins are activated by outside-in activation through integrin ligand binding, or by inside-out activation through intracellular signaling. An important question is how integrin activity is regulated, and this topic has recently drawn much attention. Changes in integrin affinity for ligand binding are due to allosteric structural alterations, but equally important are avidity changes due to integrin clustering in the plane of the plasma membrane. Recent studies have partially solved how integrin cell surface structures change during activation. The integrin cytoplasmic domains are relatively short, but by interacting with a variety of cytoplasmic proteins in a regulated manner, the integrins acquire a number of properties important not only for cell adhesion and movement, but also for cellular signaling. Recent work has shown that specific integrin phosphorylations play pivotal roles in the regulation of integrin activity. Our purpose in this review is to integrate the present knowledge to enable an understanding of how cell adhesion is dynamically regulated.

It has been demonstrated that persistent organic pollutants (POPs) can affect the immune system of mammals and birds. In this study, the concentration of different POPs and leukocytes in blood samples from three chinstrap penguin (Pygoscelis antarctica) populations was analysed in order to assess the impact on haematological parameters. Using blood sample smears, basophils, eosinophils, heterophils, lymphocytes and monocytes were quantified. Mature and immature red blood cells were counted and cell alterations in both white and red blood cells were analysed. At the same time, whole blood was analysed for POPs. The results showed that contaminants, such as dichlorodiphenyltrichloroethane and its metabolites (ΣDDT), as well as polychlorinated biphenyls (ΣPCB), had significant correlations to eosinophils, lymphocytes and heterophils. This indicates possible immunohaematological alterations derived from exposure to such contaminants. Cytological alterations were also observed, such as cytotoxic granules, toxic heterophils, and atypical and granulated lymphocytes, which would demonstrate that these seabirds are being exposed to stress agents that could be producing some alterations at a leukocytary cellular level.

Interactions between nutrition and immunity are diverse and have profound implications on animal growth and productivity. The innate immune system provides protection during the initial stages of infection and is responsible for mediating many of the alterations in nutrient metabolism. The macrophage is the key sensory and regulatory cell of the innate immune system. Their pro-inflammatory cytokines coordinate local immunity to pathogens, yet also act systemically to alter metabolic homeostasis and decrease food intake and growth rate. Altered energy, amino acid, lipid, and mineral metabolism have nutritionally important implications. For example, an innate immune response results in decreased uptake of amino acids by skeletal muscles and a corresponding increase in uptake by the liver and to a lesser extent by leukocytes. The net result is a decrease in amino acid requirements with no change in the efficiency of their use for growth. The shift in the priority of individual tissues for nutrients appears to be accomplished by changes in the types and amounts of their nutrient transporters and storage proteins. Adaptive immune responses result in considerably more subtle changes in nutrient metabolism than innate responses.

This paper reviews the current state of knowledge of the avian basophilic leukocyte. It includes a description of the general morphology of the cell derived from light and electron microscopy. The relative and absolute counts of basophils in different species are described, including the current status of the cytochemical constituents in their characteristic granules. The role of the basophil during the acute inflammatory response following exposure to non-infectious and infectious agents is examined. In birds basophils appear to play an important role in early inflammatory and immediate hypersensitivity reactions, but differ from those in mammals by not contributing to delayed hypersensitivity. They are crucial participants in cutaneous basophilic hyper-sensitivity reactions and in passive cutaneous and systemic anaphylaxis. The role of the basophil in the stress response in birds is discussed. When some birds are exposed to severe stress a basophilia develops – a physiological response that may be unique to birds.