The absence of LC and HC truncation leads to Ig aggregation. (A) Analysis of CD138⁺ cells from normal (NM), μNR (Cμ1/2 deletion), and μNRL^−/− mice, stained after sorting with PAS and hematoxylin as in Figure 5A, showed that RBs are frequently generated when LC is missing. (B) Cells were surface-stained with anti-CD138 followed by intracellular staining with anti-IgM. The ratio of IgM⁺ CD138⁺ cells is well maintained in μNRL^−/− animals (1.3%) and allows a direct comparison (C) of the RB to nuclei ratio in HC truncation mice with and without LC. ND indicates not determined.