Antibody producing B cells are vital to the immune system. The development and differentiation of B cells are complex processes that are regulated by specific cell-surface receptors. Mice expressing a chimeric heavy chain transgene, Human Immunoglobulin g1 (HUG-1) gene, are used in our studies. Hybridomas are generated from hyperimmunized HUG transgenic mice to investigate the concentration of the antibody being secreted as well as its association with Igb components of the B cell receptor (BCR). Our ultimate goal is to determine whether HUG associates with the same proteins as murine-heavy chain in the BCR. Immunoassays, such as ELISAs and Western Blots, were used to detect and examine the presence of HUG transgenic H chain, endogenous ? H chain, and k L chain in 11 different cell lines. We sought to optimize each procedure as the first step in understanding the mechanisms involved in cell signaling by the BCR and immunoglobulin chain rearrangement.