Polyclonal activation of B-cells

It was demonstrated in the BN rat that mercuric chloride induced a T-dependent polyclonal activation of B cells [181]. Helper/inducer T cells exposed to mercuric chloride either in vivo or in vitro could induce the proliferation of normal autologous T lymphocytes. Normal syngeneic Ia+ cells were necessary for this proliferation [194]. In BN rats lacking T cells, no auto-... 

T-independent immunogens (reviewed by Feldmann, 1974) usually have multiple copies of the same determinant and are, therefore, capable to react with several receptors on the same B cell ( capping ), which activates the cell. At high concentrations, T-independent immunogens may become polyclonal activators of B cells and act as mitogens of B cells. T-dependency may vary with the host haptenated polyacrylamide beads are T-independent in the mouse (Feldmann et al., 1974) and T-dependent in man (Galanaud, 1979). 

A lipopolysaccharide (LPS) is any compound consisting of covalently linked lipids and polysaccharides. The term is used more frequently to denote a cell wall component from Gram-negative bacteria. LPS has endotoxin activities and is a polyclonal stimulator of B-lymphocytes. 

Assays such as this that use polyclonal mitogens for activation may not be as sensitive as specific antigen-driven systems (Luster et al., 1988). In addition, suppression of the mitogen response does not always correlate with the PFC response. Since mitogenesis represents only a small aspect of B-cell function and maturation, this endpoint is not sensitive to early events that may affect activation, or later events that may affect differentiation of B cells into antibody-secreting cells (Klaus and Hawrylowicz, 1984). 

Bernasconi NL, Traggiai E, Lanzavecchia A Maintenance of serological memory by polyclonal activation of human memory B cells. Science 2002 298 2199-2202. 

P.A induces synthesis of polyclonal antibodies in B lymphocytes of human and mouse origin, and it is probably a T-cell-regulated polyclonal activator of human B cells. It is chemotactic, blocks heat-labile and heat-stable opsonins, activates or inhibits complement fixation (depending on the dose) and has hypertensive activity when injected in some animals and humans. 

The stems of the tree were foimd to contain polysaccharides consisting of arabinose, galactose and galacturonic acid and only minor amoimts of rham-nose. Structural studies indicate that the polymeric material consists of 1,4-linked galacturonic acid residues, terminal, 1,4-, 1,6- and 1,3,6 galactose units and terminal and 1,5-linked arabinofuranose residues. Further studies must be performed on this in order to determine what type of pectin it can be classified as. The Hnkage data indicate that both AG-I and AG-II are present. This polymer was shown to activate polyclonal B-cells [78]. 

Compared to people in a noncontaminated area, plasma IgG levels were also significantly decreased in proportion to increasing plasma levels of TCDD in a cohort exposed in an industrial accident in Seveso, Italy.118 There was no effect on IgM or IgA levels, or on complement levels IgE was not measured. In separate studies, in vitro exposure to TCDD enhanced the spontaneous production of IgE by B cells isolated from atopic but not non-atopic individuals, but did not affect the levels of other isotypes.119 Other recent studies have reported small changes in immune cells from individuals exposed occupationally to PHAH.120121 For example, compared to unexposed controls, a cohort of men exposed occupationally to TCDD had diminished IFNy production in a recall response to tetanus toxin, while IFNy production following polyclonal activation was unaffected.120 This observation is consistent with mouse studies, in which antigen-specific responses are highly suppressed by TCDD, but mitogen-driven T cell responses are less susceptible to impairment.83 88122123... 

Regarding the cellular phenomenon giving the autoimmune disease in Balb mice, the importance of T cells in the induction of the immune-complex disease was found while in another strain, SJL mice, a polyclonal B cell activation was obtained however, the importance of T cells could not be excluded [209],... 

SLE is a systemic autoimmune disorder characterized by the activation of T and polyclonal B lymphocytes, production of autoantibodies, and formation of immune complexes causing tissue and organ damage (A9). Abnormal Th cytokines are involved in the pathogenesis of autoimmune diseases (H15). Recent reports indicated that peripheral blood mononuclear cells of SLE patients show decreased in vitro production of Thl cytokines IL-2, IFN-y (F8), TNF-a (H14), and IL-12 (H13, L14, L15) with upregulation of Th2 cytokine IL-4 (F8) and IL-10 (L14). Such an imbalance of Th cytokines may account for the polyclonal B cell activation observed in SLE. An earlier report suggested that there was no relationship between in vitro production of Thl and Th2 cytokines and disease activity (B4), whereas other studies demonstrated that serum concentrations of Thl cytokines IL-12 (T6), TNF-a (D4), and IFN-y (A6) are significantly elevated in SLE patients. 

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