||The largest mass of lymphoid tissue in the body, the Gut Associated Lymphoid Tissues (GALT), is the digestive tract's immune system and stores immune cells that carry out defense attacks on pathogens. B cells, with help from T cells, begin to produce antibodies specific to the invading pathogen. In the gut, IgA is the primary receptor isotype that B cells express on their surface or secrete out in the lumen during an immune response to a pathogen. Much is known about the assembly of the B cell antigen receptor, which occurs during development in the bone marrow, the role of GALT microenvironment in shaping immune response is currently under intense investigation. Identifying proteins and unraveling mechanisms underlying B cell immunity in the GALT is critical for the rational design of oral vaccines. Ly-6A/Sca-1 (Ly-6A) is a glycosyl-phospatidylinositol-anchored surface protein, which is found on a number of cell types, including lymphocytes, is known to participate in immune response. Analysis of B cell development in the bone marrow in Ly-6A -/- mice showed sex-specific developmental defects, and Ly-6A -/- mice have significantly elevated serum levels of IgA with λ light chain than wild type controls. These observations merited further examination of the development of B cells and assessment of sex-specific alterations in the usage of λ light chain as part of IgA either expressed on the surface or secreted by B cells in the GALT. My hypothesis was that Ly-6A influences both expression of λ light chain in a sex-specific manner and receptor editing in the lamina propria of the gut. I had two specific aims; first, I investigated the sex specificity and source of IgA λ antibodies by examining cell populations in the GALT of Ly-6A -/- and wild type (control) mice. Second, I determined if editing of the antigen receptor with a bias to λ light chain usage occurs in the lamina propria (LP) of Ly-6A -/- mice. I tested my hypothesis by enumerating B cells in the LP and peyer's patches (PP) derived from female and male Ly-6A -/- and wild-type mice for cell surface expression of λ light chain using flow cytometry. I did not observe statistically significant differences in expression of λ light chain expression on the surface of B cells across the sexes and genotypes using 2-way analysis of variance (ANOVA).