BCL10, with an N-terminal caspase recruitment domain (CARD), is found in a number of apoptotic regulatory molecules. It was identified through its direct involvement in t(1;14) of mucosa-associated lymphoid tissue (MALT) lymphoma. Expression of BCL10 was shown to induce NFkappaB activation in a NIK-dependent pathway. This MAb labels subpopulations of normal B and T cells and is a useful tool for the sub-classification of lymphomas. In MALT lymphomas with the t(1;14) translocation, while 55% of MALT lymphomas lacking this translocation exhibited the same labeling pattern, although at a much lower level.