Rajani MallaAdhikari, Srijana2026-04-242026-04-242018https://hdl.handle.net/20.500.14540/26415Mast cells (MCs) are densely granulated tissue dwelling cells that are widely distributed throughout the body, especially in the periphery where there is direct contact between host and external environment including incoming antigens and pathogens. Activation of MCs leads to secretion of pro-inflammatory and immune- regulatory mediators by the process of exocytosis. Furthermore, MCs are able to regranulate secretory granules after one set of exocytosis. In this study, secretory response of MCs to multiple allergen challenges, and cytokines and chemokine expression by MCs to different treatments were analyzed. RBL2H3 mast cell line was stimulated by allergen for multiple times and its response on mediator released was analyzed by β-hexosaminidase assay. The difference in β-hexosaminidase release was significant during both challenges; secondary and tertiary when compared to primary challenge. Mast cells regranulate and degranulate again in different challenges at least up to two times and can be challenged with antigen again and again. Further, mast cells were treated with different triggers and the secretion of various pro-inflammatory cytokines (IL-4, IL5, IL-6, IL-13, TNF-α) and chemokine (MIP-α) were studied at mRNA level by using semi- quantitative RT-PCR. At first, PCR was standardized in terms of annealing temperature, number of thermocycle and amount of template for these molecules. These standardized conditions further exploited to study their expression levels in RBL-2H3 and to determine their modulation under various antigenic or pathogenic conditions. Finding suggests that MCs can be differentially activated by various triggers to release cytokines and chemokine. By understanding the nature of stimuli and specific MCs response to it, MCs can selectively be modulated during inflammatory or infectious disease conditions. Further elucidation of the molecular mechanisms involved in mast cell activation and exocytosis by different stimuli may provide new therapeutic avenues for treating allergic disorders. Key words: Mast cells (MCs), cytokines, exocytosis, allergen, β -hexosaminidase assay, RT-PCRen-USMast cellsExocytosisThesis