In patients with active systemic lupus erythematosus (SLE), a marked B lymphocytopenia was identified that affected CD19+/CD27− naive B cells more than CD19+/CD27+ memory B cells, leading to a relative predominance of CD27-expressing peripheral B cells. CD27high/CD38+/CD19dim/surface Iglow/CD20−/CD138+ plasma cells were found at high frequencies in active but not inactive SLE patients. Upon immunosuppressive therapy, CD27high plasma cells and naive CD27− B cells were markedly decreased in the peripheral blood. Mutational analysis of V gene rearrangements of individual B cells confirmed that CD27+ B cells coexpressing IgD were memory B cells preferentially using VH3 family members with multiple somatic mutations. CD27high plasma cells showed a similar degree of somatic hypermutation, but preferentially employed VH4 family members. These results indicate that there are profound abnormalities in the various B cell compartments in SLE that respond differently to immunosuppressive therapy.

Maintenance of protective humoral immunity depends on the generation and survival of antibody-secreting cells. The bone marrow provides niches for long-term survival of plasma cells generated in the course of systemic immune responses in secondary lymphoid organs. Here, we have analyzed migratory human plasma blasts and plasma cells after secondary vaccination with tetanus toxin. On days 6 and 7 after immunization, CD19 ؉ / CD27 high /intracellular immunoglobulin G high (IgG high )/HLA-DR high /CD38 high /CD20 ؊ / CD95 ؉ tetanus toxin-specific antibodysecreting plasma blasts were released in large numbers from the secondary lymphoid organs into the blood. These cells show chemotactic responsiveness toward ligands for CXCR3 and CXCR4, probably guiding them to the bone marrow or inflamed tissue. At the same time, a population of CD19 ؉ /CD27 high /intracellular IgG high /HLA-DR low /CD38 ؉ /CD20 ؊ /CD95 ؉ cells appeared in the blood in large numbers. These cells, with the phenotype of long-lived plasma cells, secreted antibodies of unknown specificity, not tetanus toxoid. The appearance of these plasma cells in the blood indicates successful competition for survival niches in the bone marrow between newly generated plasma blasts and resident plasma cells as a fundamental mechanism for the establishment of humoral memory and its plasticity. IntroductionProtective humoral memory is conferred by stable titers of specific antibodies (Abs) and can last for years. 1 Although primary contact with an antigen (Ag) leads to the formation of Ab-secreting plasma blasts (PBs) with a lifespan of less than 1 week in extrafollicular foci and results in short Ab responses, 2 most Ab-secreting cells (ASCs) generated during secondary (memory) immune response leave the follicles of the secondary lymphoid tissues as PBs. Specific ASCs are later found in the bone marrow (BM), [3][4][5] mucosa-associated tissues, chronically inflamed tissues, 6 or, to a lesser extent, the red pulp of spleens, 7 with the phenotype of mature plasma cells (PCs) and a potential lifespan of more than 18 months. 3,8,9 Indeed, specific Ab titers, mostly of immunoglobulin G (IgG) and IgA subclasses, can be stable for years 10 and are produced mainly by resident PCs of the BM. 10,11 The survival of PCs within the bone marrow (BM) is not an intrinsic capability of these cells but, rather, is regulated by the local microenvironment, 7 which provides a limited number of survival niches for PCs. [12][13][14] Because Abs of the IgG subclass have only a half-life of 3 weeks, 12-14 the survival of PCs in the BM is prerequisite for the maintenance of Ab titers over long time periods (ie, protective immunity and memory). Release from secondary lymphoid organs, migration of PBs to the BM, and competition for the apparently limited number of survival niches with resident PCs generated earlier control the establishment and persistence of protective humoral memory.Chemokines and their receptors are crucial for the control of lymphocyte trafficking. In mouse, CX-chemokine-re...

Natural killer (NK) cells are an important effector cell type for adoptive cancer immunotherapy. Similar to T cells, NK cells can be modified to express chimeric antigen receptors (CARs) to enhance antitumor activity, but experience with CAR-engineered NK cells and their clinical development is still limited. Here, we redirected continuously expanding and clinically usable established human NK-92 cells to the tumor-associated ErbB2 (HER2) antigen. Following GMP-compliant procedures, we generated a stable clonal cell line expressing a humanized CAR based on ErbB2-specific antibody FRP5 harboring CD28 and CD3ζ signaling domains (CAR 5.28.z). These NK-92/5.28.z cells efficiently lysed ErbB2-expressing tumor cells in vitro and exhibited serial target cell killing. Specific recognition of tumor cells and antitumor activity were retained in vivo, resulting in selective enrichment of NK-92/5.28.z cells in orthotopic breast carcinoma xenografts, and reduction of pulmonary metastasis in a renal cell carcinoma model, respectively. γ-irradiation as a potential safety measure for clinical application prevented NK cell replication, while antitumor activity was preserved. Our data demonstrate that it is feasible to engineer CAR-expressing NK cells as a clonal, molecularly and functionally well-defined and continuously expandable cell therapeutic agent, and suggest NK-92/5.28.z cells as a promising candidate for use in adoptive cancer immunotherapy.