IgG plasma cells display a unique spectrum of leukocyte adhesion and homing molecules

Long-lived antibody-secreting plasma cells are formed in the secondary lymphoid organs and subsequently home to the bone marrow, although the mechanisms that control this migration remain primarily unknown. In this study, we show that IgG plasma cells constitute a significant fraction of cervical lymph node cells from older mice deficient in both E- and P-selectin (E/P^-/-), and that these cells can be prospectively isolated by phenotype. These IgG plasma cells were polyclonal, cytoplasmic Ig⁺, spontaneously secreted antibody, were in the G₀/G₁ phase of the cell cycle, and failed to express multiple B-cell surface markers. The plasma cells exhibited up-regulated cell surface expression of multiple adhesion molecules, including α₄ and leukocyte function-associated antigen 1 (LFA-1) integrins, CD44, and P-selectin glycoprotein ligand 1 (PSGL-1). IgG plasma cells bound to vascular cell adhesion molecule 1 (VCAM-1) significantly better than IgM⁺ B cells, indicating that the α₄ integrins were constitutively active. A subset of IgG plasma cells also bound hyaluronic acid, the ligand for CD44. In addition, the IgG plasma cells interacted strongly with E-selectin, but poorly with P-selectin, despite elevated levels of PSGL-1 protein. The preferential interaction of plasma cells with E-selectin, but not P-selectin, correlated with elevated α1,3-fucosyltransferase-VII messenger RNA levels, but selective down-regulation of core 2 β-6-N-glucosaminyltransferase levels, compared to B cells. These results demonstrate a unique adhesion profile for murine IgG plasma cells. Furthermore, the E/P^-/- mice represent a novel system to isolate and purify significant numbers of primary IgG plasma cells.