[...]... depend on an array of cell surface receptor molecules, including Ig receptors for antigen, histocompatibility markers, receptors for the Fc region of IgG and for complement (C3b component) The T lymphocyte T lymphocytes which undergo maturation in the thymus are key cells in the expression of many facets of immunity, where they perform a variety of functions essentially concerned with immune regulation... of immunology has now become essential for the comprehension of many disease processes In addition to the awareness of an expanding spectrum of diseases which have at their core immunologic mechanisms, basic information is also required on the cells of the immune system and their interactions and effector mechanisms The immune system is extremely complex, performing a variety of activities directed... has evolved to recognize molecular conformations foreign to the individual (antigenic determinants) and to promote their elimination To accomplish this effectively, the system is ubiquitously distributed throughout body tissues and has as basic operational features: molecular recognition, amplification and memory, together with a range of effector pathways by which foreign material may be eliminated The... proportion of the expanded cell population remains dormant as memory cells and accounts for the augmented secondary response on reexposure to the same antigen Lymphocytes are divided into B and T cell classes on the basis of ontogeny and function Functionally, B lymphocytes are responsible for humoral, and T lymphocytes for cell-mediated immune responses These cells also differ in their distribution within...The relationship between pathology and medicine and easily digestible fusion in the chapters of this book These introductory remarks pave the way for the enunciation of some general principles The limited nature of clinical and pathologic responses The clinical signs resulting from malfunction of a particular... tissues and form an important component of the defense mechanism by removing micro organisms from blood and tissues Their most important characteristic is their ability to pinocytose soluble molecules and phagocytose particles Certain types have the ability also to process and present this internalized foreign material to immunocompetent lymphocytes In addition, they provide factors necessary for lymphocyte... system over an extended period, such as, for example, in chronic infections and autoimmune disease 8 Host response Immune complex disease may occur only in certain individuals who produce moderate amounts of antibody of moderate affinity Those generating high antibody titers of good affinity tend to eliminate antigen more effectively and therefore give less opportunity for immune complex deposition Type... activation of factor XII and is completed eventually by the formation of kallikrein, which acts on an a-globulin substrate, kininogen, to form bradykinin Bradykinin is a nonapeptide which produces marked and prolonged slow contractions of smooth muscle as well as dilation of peripheral arterioles and increased capillary permeability The pathway of formation of bradykinin can be inhibited in at least three... contact with appropriate antigenic determinants and then undergo transformation, proliferation and further differentiation (Fig 2.1) Ultimately, one or more effector pathways are initiated and the antigen concerned may then be eliminated Activated cells secrete a variety of biologically active effector molecules which are responsible both for cellular regulation and effector functions In addition, a proportion... momentary needs of the animal A normally functioning immune system is an effective defense against the intrusion of noxious foreign materials such as pathogenic microbial agents, toxic macromolecules and to some extent against endogenous cells which have undergone neoplastic transformation However, by virtue of its inherent complexity, the system has the potential to malfunction and, since it also has . h1" alt="" Clinicopathologic principles for veterinary medicine