Retinoids and other derivatives of vitamin A are known to have important functions in regulating differentiation and proliferation of epithelial cells. We have tried to examine the immunological effects of ATRA in colon epithelial cell lines in combination with different pro-inflammatory activators. We chose the two most potent pro-inflammatory cytokines known IL-1β and TNF-α for studying the effect of ATRA. So I used the two cytokines in the presence or absence of ATRA as inducers on Caco2 colon epithelial cell lines for 6hr. We observed that ATRA was responsible for conferring the CD103 cell surface expression patterns on DC and Mf. In case of CX3CR1 surface expression, DC treated with ATRA conditioned CEC supernatant showed an increase in CX3CR1 expression but Mf showed a decrease in CX3CR1 expression with a similar treatment. The fact that ATRA has varied effect on different cells indicates the capability of ATRA to affect the final T-lymphocyte responses. In our in vitro system we observed that ATRA treated CEC supernatant can influence the DC which when co-cultured with CD4+ T lymphocytes, TH17 cells were decreased while for Mf, the number of TH17 cells was significantly increased. Defensins represent an important group of AMP consisting of 16 – 50 amino acids, organized to a structurally conserved compact structure and associated with multiple functions in order to act as a first line of defense mechanism. The three subfamilies of defensins (α, β, θ) differ in their peptide length, location of disulphide bonds, their precursor structures and in the site of expression. Elevated levels β-defensin 3 levels in colonic mucosa of patients with ulcerative colitis suggest their role in the inflammatory response. In this study we have developed a targeted proteomics based method for the determination of defensin levels in cell lysates and cell culture supernatants. Caco2 human epithelial cells were challenged with IL-1β as an inflammatory stimulus and the levels of β-defensin 2 was analyzed in cell lysates and cell culture supernatants. The developed method was validated using qPCR, quantitative ELISA and Western blot. The gene and protein expression levels of β-defensin 2 analyzed were significantly higher in IL-1β treated samples compared to the unstimulated controls. Beside β-defensin 2, the levels of β-defensin 3, β-defensin 4 and α-defensin was examined as well and significantly higher levels of β-defensin 3 could be determined in the supernatants of activated Caco2 cells as well. Our results show that the targeted proteomics method developed here offers an alternative approach for the mass spectrometric analyses of some defensins.