LPS-Induced Migration of Peritoneal B-1 Cells is Associated with Upregulation of CXCR4 and Increased Migratory Sensitivity to CXCL12

B-1 cells, which constitute a predominant lymphocyte subset in serosal cavities and produce most of natural antibodies, are subdivided into the CD5+ B-1a and CD5- B-1b cell subpopulations, but the differential roles of B-1a and B-1b cells are not well understood. We report that B-1a cells preferentially migrate out of the peritoneal cavity and upregulate the expression of CXCR4 with heightened sensitivity to CXCL12 and CXCL13 upon LPS treatment compared to B-1b and B-2 cells. Whereas B-1a cells were slightly more abundant than B-1b and B-2 cells in the homeostatic condition, the number of B-1a cells preferentially decreased 48 hr after LPS treatment. The decrease in the peritoneal B-1a cell number was accompanied with increased migration of B-1a cells toward CXCL-12 and CXCL-13 in in vitro transmigration assay using peritoneal B cells from LPS treated mice. The expression level of CXCR4, but not of CXCR5, was also more prominently increased in B-1a cells upon LPS stimulation. LPS-stimulated B-1a cells did not accumulate in omental milky spots in contrast to B-2 cells. These results suggest that B-1a cells actively migrate out of the peritoneal cavity through the regulation of the migratory responsiveness to chemokines and actively participate in systemic immune responses.

Defects in blood dendritic cell subsets in HIV-1 subtype C infected Indians.

Background & objective: DCs trigger both innate and adaptive immune responses to control HIV infection and represent a viral reservoir acting as target and HIV carriers for infection of permissive CD4+ T-cells. DCs thus form a very attractive study subject to further our existing knowledge of HIV induced immunopathogenesis due to its diverse and crucial role in HIV infection establishment, viral dissemination, immune evasion, viral persistence, etc. We aimed to characterize the effect of HIV infection on myeloid and plasmacytoid dendritic cell subsets in a group of HIV-1 subtype C infected treated or untreated Indian individuals. Methods: Blood DC subset numbers and immunophenotype were studied for 79 HIV infected subjects at various stages of disease and compared with 13 HIV-uninfected controls. Comparisons were also made between groups of subjects based on their CD4+ T cell counts and also experience of antiretrovirals. Results: Significant decreases were observed in blood DC counts and the two DC subsets in HIV infected individuals. Subjects with lowest CD4+ T cell counts also had a drastically reduced DC subset pool which correlated positively with plasma viraemia and negatively with CD4+ T cell counts. DC subsets from HIV infected subjects showed higher expression of co-stimulatory molecules CD40 and CD86, and HIV-1 co-receptors CXCR4 and CCR5 which correlated positively with HIV-1 plasma viraemia. The alterations in blood DCs were partly resolved in ART receiving study subjects. Interpretation & conclusions: Correlation between DC subset activation state and viraemia supports the role of DC activation on viral replication and CD4+ T cell depletion.

Homing-Associated Cell Adhesion Molecules and Cell Cycle Status on the Nucleated Cells in the Bone Marrow, Mobilized Peripheral Blood and Cord Blood

Homing-associated cell adhesion molecules (H-CAM) on the CD34+ cells play an important role for the engraftment process following hematopoietic stem cell transplantation (HSCT). However, it seems that not only CD34+ cells but also other nucleated cells (NCs) with H-CAM could be implicated in the engraftment process and the proliferation of hematopoietic stem cells. We investigated the differences of HCAM and cell cycle status on the NCs in cord blood (CB), bone marrow (BM), and mobilized peripheral blood (PB). The proportions of CXCR4+ cells within the NC populations were greater in CB than in PB or BM (p=0.0493), although the proportions of CXCR4+, CD44+, and CD49d+ cells within the CB CD34+ cell populations were same within BM or PB. A lower proportion of CD34+CD49d+ cells within the CD34+ cell populations was more noted in CB than in PB or BM (p=0.0085). There were no differences in cell cycle status between CB and BM or PB. Our results suggest that the migrating potential of CB would be enhanced with increased CXCR4 expression on the NCs, but the adhesion potential of CB CD34+ cells would be less than that of PB and BM. These findings may help explain why the lower cell dose is required and engraftment is delayed in cord blood stem cell transplantation.

Stem Cells Expressing Homing Receptors Could be Expanded From Cryopreserved and Unselected Cord Blood

We assessed the cytokine combinations that are best for ex vivo expansion of cord blood (CB) and the increment for cell numbers of nucleated cells, as well as stem cells expressing homing receptors, by an ex vivo expansion of cryopreserved and unselected CB. Frozen leukocyte concentrates (LC) from CB were thawed and cultured at a concentration of 1x10(5)/mL in media supplemented with a combination of SCF (20 ng/mL)+TPO (50 ng/mL)+FL (50 ng/mL)+/-IL-6 (20 ng/mL)+/-G-CSF (20 ng/mL). After culturing for 14 days, the expansion folds of cell numbers were as follows: TNC 22.3+/-7.8~26.3+/-4.9, CFU-GM 4.7+/-5.1~11.7+/-2.6, CD34+CD38- cell 214.0+/-251.9~464.1+/-566.1, CD34+CXCR4+ cell 4384.5+/-1664.7~7087.2+/-4669.3, CD34+VLA4+ cell 1444.3+/-1264.0~2074.9+/-1537.0, CD34+VLA5+ cell 86.2+/-50.9~ 113.2+/-57.1. These results revealed that the number of stem cells expressing homing receptors could be increased by an ex vivo expansion of cryopreserved and unselected CB using 3 cytokines (SCF, TPO, FL) only. Further in vivo studies regarding the engraftment after expansion of the nucleated cells, as well as the stem cells expressing homing receptors will be required.