Accessory cells

Diphenylhydantoin, which has been demonstrated to cause autoimmune phenomena in man (SLE, vasculitis and scleroderma and skin) has also been tested (via drinking water for 6 months) in genetically predisposed mice (C57BL/6-lpr/lpr strain) but the compound depressed rather than increased the levels of ANA (55 and section 4.1, below). In another study [56], a slight shift towards a Th2 response was demonstrated as an increase in the KLH-induced production of IL-4 and IgE (IgE was detected by direct ELISA, which makes these data suspect) in a 4 weeks exposure study. In this same study, proliferative responses of splenocytes to KLH (using spleen cells of KLH-sen-sitized mice), mitogens (ConA, LPS) or anti-CD3 were also reduced, possibly through interference with accessory cell function. 

Szabo, G. et al., Reduced alloreactive T-cell activation after alcohol intake is due to impaired monocyte accessory cell function and correlates with elevated IL-10, IL-13, and decreased IFNgamma levels, Alcohol Clin. Exp. Res., 25, 1766, 2001. 

Pisam, M., Prunet, P. and Rambourg, A. (1989). Accessory cells in the gill epithelium of the freshwater rainbow trout Salmo gairdneri, Am. J. Anat., 184, 311-320. 

Type IV Delayed-type Hypersensitivity (DTH). Delayed-type hypersensitivity reactions are T-cell mediated with no involvement of antibodies. However, these reactions are controlled through accessory cells, suppressor T cells, and monokine-secreting macrophages, which regulate the proliferation and differentiation of T cells. The most frequent form of DTH manifests itself as contact dermatitis. The drug or metabolite binds to a protein in the skin or the Langerhans cell membrane... 

Type IV hypersensitivity responses are elicited by T lymphocytes and are controlled by accessory cells and suppressor T cells. Macrophages are also involved in that they secrete several monokines, which results in proliferation and differentiation of T cells. Thus, there are numerous points along this intricate pathway in which drugs may modulate the final response. To achieve a Type IV response, an initial high-dose exposure or repeated lower-dose exposures are applied to the skin the antigen is carried from the skin by Langerhans cells and presented to cells in the thymus to initiate T-cell proliferation and sensitization. Once sensitized, a second challenge dose will elicit an inflammatory response. Thus, before sensitivity can be assessed, each of the models used to evaluate dermal hypersensitivity requires as a minimum ... 

Tang A. Udey MC Doses of ultraviolet radiation that modulate accessory cell activity and ICAM-1 expression are ultimately cytotoxic for murine epidermal Langerhans cells. J Invest Dermatol 1992 99 71S-73S. 

Punnonen J. De Waal Malefyt R, Van Vlasselaer P. Gauchat J-F, De Vries JE IL-10 and viral IL-10 prevent IL-4-induced IgE synthesis by inhibiting the accessory cell function of monocytes. J Immunol 1993 151 1280-1289. 

Gastric juice is the product of several cell types. The parietal cells produce hydrochloric acid, chief cells release pepsinogen, and accessory cells form a mucin-containing mucus. 

Previous studies on the effects of N=0 production on the alloimmune response utilized bulk populations of responder and stimulator cells. In order to more clearly define the circumstances that induce -N=0 synthesis in allogeneic macrophage-lymphocyte cocultures, mouse splenocyte populations were depleted of accessory cells (>90% Thy 1.2+) and cultured with mitomycin-C-treated macrophage cell lines, as the alloantigen presenting cells. The P388D1 (H2 ) and RAW 264.7 (H2 ) macrophage lines were selected because... 

Barrett, A. W., Ross, D A., and Goodacre, J. A (1993) Purified human oral mucosal Langerhans cells function as accessory cells in vitro Clin Exp Immunol 92,158-163... 

The major immunobiological effect of IL-10 is the regulation of the TH1/TH2 balance. TF cells are involved in cytotoxic T-cell responses whereas TH2 cells regulate B-cell activity and function. IL-10 is a promoter of TH2 response by inhibiting IFN-y production from THi cells. This effect is mediated via the suppression of IL-12 synthesis in accessory cells. IL-10 is involved in assisting against intestinal parasitic infection, local mucosal infection by costimulating the proliferation and differentiation of B cells. Its indirect effects also include the neutralization of bacterial toxins. 

Rakha, N.K., Dixon, J.B., Carter, S.D., Craig, P.S., Jenkins, P. and Folkard, S. (1991) Echinococcus multilocularis antigens modify accessory cell function of macrophages. Immunology 74, 652-656. 

In summary, highly reactive metabolites of Cy disrupt DNA synthesis, thus inhibiting cell proliferation. As a result, production of lymphocytes and accessory cells is suppressed, and host immunocompetence is compromised. As noted below and summarized in Table 32.5, for a number of immunosuppressive compounds a metabolic product rather than the parent compound is responsible for the toxicity. 

CD4 nonpolymoiphous glycoproteins belonging to immunoglobulin superfamily. Expressed on surface of T helper cells, accessory cells, macrophages and serves as co-receptor in MHC class B-restricted antigen induced T cell activation. Major receptor for IHV-1. 

Kradin, RL., McCarthy, K.M., Xia, W.J., Lazarus, D. and Schneebetger, E.E. (1991). Accessory cells of the lung. I. Interferon-gamma increases la" dendritic cells in the lung without augmenting their accessory activities. Am. J. Respir. Cell. Mol. Biol. 4, 210-218. 

T lymphocyte antigen receptor (TCI signalling in isolation is not sufficient to activate T lymphocytes, since purified T lymphocytes do not secrete IL-2 in response to mitogenic lectins or anti-TCR antibodies in the absence of viable accessory cells, despite the feet that under these conditions TCR-associated second... 

Experiments investigating co-stimulation have been based on the premise that TCR-mediated and costimulatory signals could be provided by ligands present on different surfaces. For example, the TCR-mediated signal could be provided to the T lymphocyte by anti-TCR antibody immobilized on a plastic surface and the co-stimulatory signal by any accessory cell of interest. This approach has been used (Mueller et a.1., 1989) to identify several features of the co-stimulatory signal. 

It is delivered by T lymphocyte/accessory cell contact, not by soluble factors such as cytokines. 

It does not require MHC compatibility between the responding T lymphocyte and the co-stimulating accessory cell. 

These data suggest either that CDS" T cells inhibit CD4 T cell development in an unrestricted manner, or that there were different populations of CD8 T cells that exerted differential effects on ThI and Th2 CD4 T cell development. Clearly, this will not be resolved until more CD8 T cells have been cloned and the effects of these clones on CD4 T cell development determined. The feet that immunoregulatory CDfl" T cells appear to be active early in the immune response places these cells in an ideal position to influence the direction that the response will take. However, how CDS" T cells are recruited and activated, how they interact with accessory cells and recognize antigen, and how they mediate their effects, have yet to be determined. 

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