T and B cell, interaction

The NHR contains also the conserved Calcineurin docking site, PxlxIT, required for the physical interaction of NEAT and Calcineurin. Dephosphorylation of at least 13 serines residues in the NHR induces a conformational change that exposes the nuclear localization sequences (NLS), allowing the nuclear translocation of NEAT. Rephosphorylation of these residues unmasks the nuclear export sequences that direct transport back to the cytoplasm. Engagement of receptors such as the antigen receptors in T and B cells is coupled to phospholipase C activation and subsequent production of inositol triphosphate. Increased levels of inositol triphosphate lead to the initial release of intracellular stores of calcium. This early increase of calcium induces opening of the plasma membrane calcium-released-activated-calcium (CRAC) channels,... 

The unique domain following the SH4 domain from the N-terminus is a region with considerable variation in the amino acid sequences among different Src family members. This unique domain may be involved in protein-protein interactions. For example, the unique region of Lck is linked to CD4 and CD8, while those of Fyn and Lyn may be associated with the T- and B-cell antigen receptors. 

ECM is facilitated by small hyaluronic acid molecules implies a function in host defense, but has not been proven (106). Increased levels of hyaluronic acid were associated with colon inflammation, psoriasis, osteoarthritis, rheumatoid arthritis, and scleroderma (101,107,108), as well as with viral infections (109). Hyaluronic acid is produced by endothelial cells and binds to its receptor, CD44, expressed by activated T and B cells, inducing the attachment of the two cell types (110). This interaction is controlled by the expression of specific hyaluronic acids sub-types or by modifications of CD44 on platelets (111). High molecular weight hyaluronic acid and CD44 are essential for scarless embryonic wound repair (112). 

Up to a certain degree, an increase in the dose (weight) of antigen will increase antibody titer however, this may also increase crossreactivity. Adjuvants also increase the immunogenicity of proteins. Haptens should be labeled with carrier proteins to elicit an immune response. The carrier protein should be foreign to the host to be recognized by the T-cells. For most immunogens, the interaction of T- and B-cells is essential for antibody production. 

Figure 4.8 Failure of physiological cooperative interactions to occur in vivo between T and B lymphocytes differing at the major histocompatibility locus. The scheme followed is described in text. Recipients for all cell combinations were (A x B10)Fi hybrids. Combinations and strain origins of T and B cells and the relevant genetic differences are indicated. Recipients in groups I—VIII were secondarily challenged with 50 pg of DNP—BGG. Mean serum anti-DNP antibody levels of groups of five mice on day 7 after secondary challenge are illustrated. Horizontal bars represent ranges of the standard error. (Taken from reference 64.)...

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