We investigated the structure of the pre-B cell receptor (preBCR) that plays a crucial role in the development and binding properties of an antibody. We used mouse pre-B cell hybridoma subclones that had a human gamma (g) transgene (HUG1). HUG replaces the endogenous mouse heavy chain constant region. The hybridomas also had a J gene segment deletion, disabling expression of the endogenous mouse heavy chain. We probed into the effect of HUG on kappa (k) light chain expression and its associations with other components of the preBCR. ELISAs and Western blots were used to verify expression and quantify amount of kappa produced in seven HUG<sup>+ </sup>JH knockout cell lines. Optimization of conditions pertaining to different steps in the assays proved to be a crucial step in our investigation into light chain gene rearrangement.