Components of the immune system

T-Lymphocytes (4,5) and other cellular components of the immune system also have equally wide implications in regulation of the normal immune system. The T-lymphocytes play a central role in the body s response to harmful antigens and tumor—host interaction (4). Responses involve antigens derived from vimses, bacteria, parasites, and tumors. T-ceUs also participate in the immune surveillance response, where self-antigens are recognized, but usually sequestered within the cell and, when exposed, become markers of cellular damage. 

Scherphof, G., Damen, J., and Hoekstra, D. (1981). Interactions of liposomes with plasma proteins and components of the immune system, in Liposomes From Physical Structure to Therapeutic Applications (C. G. Knight, ed.), Elsevier, Amsterdam, pp. 299-322. 

Other investigators have been unable to demonstrate lead-induced effects on various components of the immune system in laboratory animals. The effects of lead exposure of varying duration on natural killer cell and T-lymphocytc function were investigated in rats. Male Alderly Park rats received lead as lead acetate in the drinking water at lead concentrations equivalent to 14.3 and 143 mg lead/kg/day for... 

There are normally 4000 to 11,000 leukocytes (white blood cells) per microliter of human blood. However, leukocytes act primarily within the tissues those found in the blood are actually in transit. Leukocytes are also found in lymphoid tissues such as the thymus, spleen, and lymph nodes. These cells are referred to as "white" blood cells because they lack hemoglobin and are essentially colorless. Leukocytes are an important component of the immune system. General inflammatory and immune functions of these cells include ... 

Antigens usually are macromolecules that contain distinct antigenic sites or epitopes , which can be recognized and interact with the various components of the immune system. They can exist as individual molecules composed of synthetic organic chemicals, proteins, lipoproteins, glycoproteins, RNA, DNA, polysaccharides—or they may be parts of cellular structures (bacteria or fungi) or viruses (Male et al., 1987 Harlow and Lane, 1988). 

HIV infects and destroys T-helper lymphocytes, i.e. it directly attacks an essential component of the immune system itself. 

RA results from a dysregulation of the humoral and cell-mediated components of the immune system. Most patients produce antibodies called rheumatoid factors these seropositive patients tend to have a more aggressive course than patients who are seronegative. 

Psychological stress may influence the immune system by activation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic-adrenal-medullary axis (SAM). The well-described innervation of primary and secondary lymphoid tissues by the autonomic nervous system also has been implicated in stress-related modulation of the immune response. These pathways operate by producing biological mediators that interact with and affect cellular components of the immune system.13... 

TABLE 15.4. Cellular Components of the Immune System and Their Functions... 

Host-resistance assays can be used to assess the overall immunocompetence of the humoral or cell-mediated immune systems of the test animal (host) to fend off infection with pathogenic microbes, or to resist tumorigenesis and metastasis. These assays are performed entirely in vivo and are dependent on all of the various components of the immune system to be functioning properly. Thus, these assays may be considered to be more biologically relevant than in vitro tests that only assess the function of cells from one source and of one type. Since these assays require that the animal be inoculated with a pathogen or exogenous tumor cell, they cannot be performed as part of a general preclinical toxicity assessment, and are thus classified as Type 2 tests in the revised Redbook. These assays are also included as Tier II tests by the NTP. 

Specific cell types of humoral components of the immune system can be isolated and studied. 

Molecular components of the immune system 1.3.1 Properties of antibodies... 

Interestingly, infections by commonly occurring bacteria (such as those in the lower intestine) do not generally occur in adult AIDS patients, perhaps because components of the immune system responsible for controlling the common bacteria are less affected by HIV infection. However, children bom infected with AIDS often do develop lung infections with common bacteria. In addition, adult AIDS patients may experience infections with tuberculosis-like bacteria. 

---