| Summary: | The symptomology associated with allergic diseases are a direct consequence of the release of pro-inflammatory mediators from mast cells following bi- or multivalent antigen cross-linking with the high affinity immunoglobulin (Ig) E receptor, FcεR1. Chemokines, small 8-15 kDa polypeptides, control the activation and recruitment of immune cells during the allergic response. Previous studies have demonstrated that co-stimulation by the chemokine, macrophage inflammatory protein-1α (Mip-1α) and cross-linking by IgE with antigen result in four phenomenon 1) enhanced degranulation in ex vivo conjunctival mast cells and rat basophilic leukemia (RBL-2H3) cell line via its chemokine receptor (CCR) 1, cell line also referred to as RBL-CCR1; 2) arrested Mip-1α-induced chemotaxis of RBL-CCR1 cells; 3) enhanced production of proinflammatory mediators from RBL-CCR1 cells and 4) enhanced gene expression in RBL-CCR1 cells of regulatory molecules downstream of CCR1 and FcεR1 signaling pathways, Regulator of G-protein Signaling (RGS)-1 and Tribbles (TRB)- 3. It has therefore been proposed that co-engagement of CCR1 and FcεR1 affects other mast cell processes such as chemotaxis, and moreover these data indicate cross-talk between CCR1 and and FcεR1 signaling pathways. Chemotaxis of mast cells to sites of inflammation and the subsequent release of pro-inflammatory mediators are key to eliciting allergic response. Although there is a vast amount of information pertaining to the molecular mechanisms of chemotaxis in several cell types, there is very little evidence to understand mast cell chemotaxis at this level. Based on current knowledge, the main objective of this thesis was to investigate 1) the effect of CCR1 and FcεR1 co-engagement on mast cell motility and 2) the role of RGS1 and TRB3 on mast degranulation, mediator release and chemotaxis. The data obtained from this thesis is the first to demonstrate the role of WASP, CCR1 and actin polymerisation as mechanisms underlying Mip-1α induced RBLCCR1 chemotaxis, using real time microscopy. Moreover, CCR1 and FcεR1 engagement inhibits RBL-CCR1 actin cytoskeletal re-organisation and significantly increases other cell motility parameters such as directionality and Euclidean distances which are required for efficient Mip-1α-induced chemotaxis. Also, by using a murine model of allergic conjunctivitis, conjunctival mast cells accumulate in the forniceal area of an inflamed conjunctiva in comparison to non-diseased vi mice. In addition, by using siRNA the present study is also the first to show that RGS1 and TRB3 serve as negative regulators of RBL-CCR1 degranulation, mediator release and chemotaxis upon CCR1 and FcεR1 engagement. In conclusion, the data presented in this thesis could advance our understanding of the mechanisms responsible for mast cell migration and arrest during an allergic response, and hence provide new targets for anti-allergic drugs.
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