Suppressor cells

In addition to antibodies, the immune system also consists of bone-marrow derived lymphocytes, or B cells, and T cells that come from the thymus gland, both of which (indirectly) produce antibodies. These cells, in turn, may be helped by helper cells (= H) and suppressed by suppressor cells (= S). Helper cells may be alarmed as to the presence of antigens by macrophages (= M) that eat the antigens and leave parts of their meal on their cell surface. 

We can interpret these equations in the following way. The first line assures us that antibodies will be present only when B cells, helper cells and antigens are all present. The second line states that B cells will grow if antigens and/or B cells are present and if helped by helper cells. The third line indicates that helper cells arise either if other helper cells ai e present or, if no suppressor cells are present, if there are any antigens. The fourth line yields suppressor cells if suppressor cells are already present and/or there are any helper cells. The last line implies that the antigen remains if there are no antibodies or vani.shes if antibodies are present. Since concentrations cannot exceed 1, it is understood that, in the above equations, 1 + 1 = 1. 

Now suppose the body s immune system malfunctions and begins attacking the body itself. A typical scenario might involve killer cells K attacking helper and/or suppressor cells. Chowdbury and Stauffer [chowdQO] developed a simple five-cell model using two types of helper cells Hi and H2). two type of suppressors Si and S2) and one killer cell (K) ... 

An increased ratio of T suppressor cells to T helper cells was seen in mice given 2.5 and 5.0 mg/kg/day of methyl parathion for 15 days the spleen to body weight ratio was increased at 5 mg/kg/day (Tian et al. 1997). No other immunological or lymphoreticular end points were measured. 

Non-specific defence mechanisms 4.6.2 Suppressor cells (Ts cells)... 

Most T-helper cells express a membrane protein termed CD4 on their surface. Most T-cytotoxic and T-suppressor cells produce a different cell surface protein, termed CD8. Monoclonal antibodies specifically recognizing CD4 or CD8 proteins can thus be used to differentiate between some T cell types. 

Fisher, M. S. and Kripke, M. L., Further studies on the tumor-specific suppressor cells induced by ultraviolet radiation, J. Immunol. 121, 1139-1144, 1978. 

Schmitt, D. A., Owen-Schaub, L., and Ullrich, S. E., Effect of IL-12 on immune suppression and suppressor cell induction by ultraviolet radiation, J. Immunol. 154, 5114—5120, 1995. 

Depletes or functionally impairs T cells enhances macrophage suppressor cell increases infections and tumorigenesis... 

SOD ha T cell Tc TcR TGA Th TLC TMP/SMX TNF Ts TX U V domain VLA Ml H m superoxide dismutase half-life thymus-derived lymphocyte cytotoxic T cell T-cell receptor thymine-guanine-adenine T helper cell thin layer chromatography trimethoprim/sulphamethazole tumour necrosis factor T suppressor cell thromboxane unit variable domain very-late antigen microlitre (10 6 litre) micrometre (10"6 metre)... 

There is also considered to be a population of T suppressor cells which acts to down-regulate both T helper cells and B cells, whether through antigen-specific or idiotype-specific mechanisms. The epitopes on the lymphocyte receptor (id-iotype) recognized by the receptor on another lymphocyte (anti-idotype) can form a network of interactions through which suppression may be mediated. 

CD8 + T cells are driven by MHC class I molecules and do not require professional APC. CD 45 Ro + CD8 + T cells are increased in early infection and are often maintained in symptomatic disease however, dendritic cells are important in stimulating cytotoxic T lymphocyte (CTL) responses in unprimed CD8 + T cell. CD8 cells may also be subdivided based on their cytokine secretion. CD8 CTL clones produce INF-y, IL-6, TNF-a, and ILIO, whereas suppressor cells produce high levels of cytokines associated with Th-2 cells, including IL-4 and low levels of IL-5, IL-6, and IL-10. 

T cells are lymphocytes produced by the thymus gland. There are two types of T cells involved in immune response CD4+ (CD positive, helper cells) and CD8 (CD positive, also called T killer, or suppressor, cells). When the APCs present the antigens to CD4+ helper T cells, the secretory function is activated and growth factors such as cytokines are secreted to signal the proliferation of CD8" killer cells and B cells. When the CD8" ... 

Steinman RM, Hawiger D, Nussenz-weig MC Tolerogenic dendritic cells. Annu Rev Immunol 2003 21 685-711. Schwarz T 25 years of UV-induced immunosuppression mediated by T cells - from disregarded T-suppressor cells to highly respected regulatory T cells. Photochem Photobiol 2008 84 10-18. 

Table 1. Suppression of cell-mediated immunity by CD8+ suppressor cells... 

Induction of Splenic CD8-I- Suppressor Cells via the Eye s Anterior Chamber... 

Fig. 1. Organ/cellular pathways in the induction of CD8+ suppressor cells by the injection of antigen into the anterior chamber (AC). he injection of antigen into the AC induces a recruitment of F4/80+ monocytic cells to the iris. Interactions with iris monocytic cells, antigen and GF-p in aqueous humor induces an immunosuppressive phenotype in the recruited cells. hese cells then recirculate from the AC to the thymus and the spleen. In the spleen, F4/80+ cells interact with B cells, peripheral NK cells, recent thymic NK emigrants and CD8+ cells with the generation of CD8+ suppressor cells that effect the suppression of a D FI reaction.

Fig. 2. Sympathetic neurons influence the development or activity of CD8+ suppressor cells. Sympathetic neurons are a source of neuropeptide Y (NPY), norepinehprine (NE) or tissue plasminogen activator (t-PA) that respectively, (i) activate IL-12, IFN-7 necessary for the activity of suppressor cells, (ii) NK cells required to generate CD8+ suppressor cells after the injection of antigen into the AC, (ill) the conversion of plasminogen to plasmin that activates immunosuppressive GF-p produced by the CD8+ suppressor cells.

Fig. 3. Proposed suppressive mechanism of CD8+ suppressor cells. The TCR of suppressor cells engages Qa-1/peptide (TCR V-region ) on a T effector cells or antigen presenting cells. CD94/NKG2A also engages Qa-1. Engagement of the entire complex triggers the secretion of TGF-p by the suppressor T cell that suppresses the effector cell that induces the DTH reaction.

Niederkorn JY, Streilein JW Characterization of the suppressor cell(s) responsible for anterior chamber-associated immune deviation (ACAID)-induced in BALB/c mice by P815 cells. J Immunol 1985 134 1381-1387. 

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