Purification of human lamina propria plasma cells by an immunomagnetic selection method.

Plasma cells (PC) are the terminal stage of B-lymphocyte differentiation and, as such, they are dedicated to large-scale secretion of antibodies (Ab). Bone marrow (BM) and lamina propria (LP) become the final reservoirs of PC generated in response to systemic and mucosal antigen stimulation, respectively. Although the majority of human PC are held in the mucosa LP, they have received less attention than PC present in other locations. A key step for many PC studies is the design of isolation protocols to purify them. A purification procedure for LPPC has not been described as yet and, therefore, we decided to develop a protocol for this purpose, comprising three main steps: (1) dissecting LP from colonic tissue; (2) releasing LP cells by a short 15-min collagenase digestion; (3) isolating LPPC by positive immuno-magnetic selection using the distinctive expression of CD54 (ICAM-I) on LPPC. By following this protocol, a viable, highly purified LPPC fraction can be obtained in less than 2 1/2 h.

Persistent polyclonal B lymphocytosis: an expansion of cells showing IgVH gene mutations and phenotypic features of normal lymphocytes from the CD27+ marginal zone B-cell compartment.

Persistent polyclonal B-cell lymphocytosis (PPBL) is an unusual and benign lymphoproliferation characterized by a polyclonal expansion of B lymphocytes, whose nature remains undetermined. The phenotypic analysis of three cases revealed that these cells were CD27+ IgM(high) CD21(high) CD5(low) and CD23(low), a phenotype associated with the normal marginal zone (MZ) B-cell compartment. As MZ B cells have initiated immunoglobulin (Ig)V gene somatic mutations, PPBL IgVH genes were sequenced. An average of 73% of these sequences were mutated. The mean number of mutation per sequence was 6.9, a number similar to those observed in the MZ B-cell compartment.