Characterization of a new antigen expressed by B and myeloid lineage cells identified by the monoclonal antibody LIP-6

Splenic marginal zone lymphomas of mice

Splenic marginal zone lymphomas (MZLs) have been found to occur at a high frequency in NFS.N mice congenic for high-expressing ecotropic murine leukemia virus (MuLV) genes from AKR and C58 mice. Based on morphological, immunological, and molecular studies of these mice, MZL is clearly recognizable as a distinct disease with a characteristic clinical behavior. MZL was staged according to the degree of accumulation and morphological change of cells within the splenic marginal zone, as follows: 1) a moderate increase in normal-looking MZ cells, judged to be prelymphomatous, and 2) MZL in three variants: i) distinct enlargement of MZ by normal-looking cells (MZL), ii) distinct enlargement of MZ by basophilic centroblast-like cells (MZL+), and iii) extensive splenic involvement by centroblast-like cells (MZL++). The rate of mitosis and apoptosis increases with lymphoma grade. In most cases, emergence of a dominant IgH clonal pattern in paired splenic biopsy and necropsy samples was correlated with progression. MZLs were transplantable and homed to the spleen. MZL may constitute a commonly occurring lymphoma type unrecognized, in part, because of the centroblastic morphology of high-grade MZL and possible overgrowth of lower-grade MZL by more aggressive follicular lymphomas.

Neoteny in lymphocytes: Rag1 and Rag2 expression in germinal center B cells

The products of the Rag1 and Rag2 genes drive genomic V(D)J rearrangements that assemble functional immunoglobulin and T cell antigen receptor genes. Expression of the Rag genes has been thought to be limited to developmentally immature lymphocyte populations that in normal adult animals are primarily restricted to the bone marrow and thymus. Abundant RAG1 and RAG2 protein and messenger RNA was detected in the activated B cells that populate murine splenic and Peyer's patch germinal centers. Germinal center B cells thus share fundamental characteristics of immature lymphocytes, raising the possibility that antigen-dependent secondary V(D)J rearrangements modify the peripheral antibody repertoire.