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Chronic lymphocytic leukemia of B-cell origin (B-CLL) is a disease with a variable clinical course, despite the fact that the neoplastic cells in this disorder are homogeneous with respect to morphology, immunophenotype, and cell cycle stage. To further investigate the heterogeneity observed in the clinical behavior of B-CLL, we determined the pheno-type and growth requirements of clonogenic cells from 28 patients with B-CLL from low-, intermediate-, and high-risk groups as defined by the Rai staging system. Using methyl-cellulose as a semi-solid media with feeder cells and/or growth factors, colonies were observed with one or more of the culture conditions tested in 25 of 28 CLLs. Pheno-typic analysis of colonies demonstrated that the clonogenic cells uniformly expressed la, CD19, CD20, CD5, and the identical light chain as the original CLL cell cultured. However, heterogeneity was observed in clonogenic B-CLL cell growth among the three different CLL risk groups. Clonogenic cells from patients with low-risk CLL required either irradiated unstimulated T cells, with or without conditioned media (CM) or irradiated activated T cells alone for colony formation. Both the number of colonies (227 ±15) as well as the number of cells per colony (220 ± 82) were large, with a mean cloning efficiency of 0.39%. In contrast, clonogenic cells from patients with intermediate- and high-risk CLL required the combination of both irradiated activated T cells and CM. As compared with the low-risk CLLs, both the number and size of the colonies formed by the intermediate- (74 ± 17, 70 ± 39) and high- (83 ± 28, 40 ± 14) risk groups were significantly lower (P< .0001). Similarly, the mean cloning efficiency was significantly reduced to 0.15% and 0.14%, respectively. None of the recombinant cytokines (interleukin 1 (IL-1] to IL-7, tumor necrosis factor, α and γ-interferon, B-cell growth factor, and granulocyte macrophage colony-stimulating factor) alone or in combination with each other could entirely replace the stimulatory effect of the activated T cells. These data suggest that clinical progression of B-CLL is associated with a loss of clonogenic potential in the circulating pool of neoplastic cells, which require as yet undefined factors provided by activated T cells and CM.

In the present report we have attempted to examine immunologic reconstitution following high-dose chemoradiotherapy and anti-B-cell monoclonal antibody (MoAb)-purged autologous bone marrow transplantation (ABMT). By cell-surface phenotypic analysis, the majority of patients had normal percentage of natural killer cells (NK), monocytes, and CD8+T cells at one month post-ABMT. In contrast, the percentage of CD4* T cells was reduced for at least 3 years, and the CD4:CD8 ratio reflected this imbalance. B-cell reconstitution was slightly prolonged, with normal percentage and absolute numbers of CD20+ B cells evident by 3 months. Although B cells returned by 3 months, in vitro assessment of B-cell function demonstrated impairment of proliferative responses to either anti-immunoglobulins bound to beads (anti-Ig), Epstein-Barr virus (EBV), or interleukin-2 (IL-2) for approximately 1 year and low molecular B-cell growth factor (BCGF) for approximately 2 or more years. Moreover, in vivo B-cell reconstitution demonstrated a more selective defect, with normal levels of immunoglobulin IgM returning at 6 months, IgG at 12 months, and IgA after 2 years. Despite normal numbers of B cells and relative normal levels of Ig early following ABMT, our in vitro data suggest an intrinsic defect in B-cell responsiveness. Moreover, these defects are similar to those observed following nonpurged autologous and allogeneic BMT, although the interval of immune impairment appears more prolonged.

In germinal centers, B lymphocytes are intimately associated with follicular dendritic cells (FDCs). It has been hypothesized that FDCs are involved in the regulation of B-cell growth and differentiation through cell-cell interactions. In this study, highly enriched preparations of FDCs were isolated by cell sorting using the FDC restricted monoclonal antibody DRC-1. When irradiated FDCs were cultured with mitogen stimulated B cells, B cell 3H-TdR uptake was inhibited by up to 80%. This inhibitory effect was not seen when paraformaldehyde fixed FDCs were added to B-cell cultures, suggesting that the FDCs needed to be metabolically active. Moreover, supernatants from cultured FDCs were similarly able to inhibit B-cell proliferation. These results demonstrate that FDCs may downregulate the clonal expansion of B cells that occurs within lymphoid follicles as part of the normal physiologic immune response. Potentially, the loss of the inhibitory role of FDCs in vivo may be of importance in certain infectious and neoplastic processes in which germinal centers are affected.

Hematologic engraftment and immune reconstitution were examined in patients who received cyclophosphamide and total body irradiation therapy followed by infusion of autologous bone marrow purged with anti-B1 monoclonal antibody (MoAb) and complement as therapy for non-Hodg-kin' 's lymphoma. Hematologic engraftment was prompt with return of ≥ 0.5 × 103/µl granulocytes and ≥ 2 × 104/µL platelets at a median of 26 and 29 days posttrans-lant, respectively. Immunologic reconstitution, in contrast, was prolonged. Normal numbers of circulating B cells were consistently noted by five months posttransplant, whereas return of normal immunoglobulin levels in some patients did not occur for one year. Normal numbers of T cells were evident within the first month posttransplant, but a reversed T4:T8 ratio persisted in some patients up to three years. In vitro responses of either B cells to triggers of activation or of T cells to mitogens and antigens were not normal for at least three months posttransplant. Natural killer (NK) cells predominated early after transplant and may demonstrate cytotoxicity against tumor cells. Our studies demonstrate that transplantation with anti-B1 purged autologous bone marrow results in complete hematologic and delayed immunologic engraftment. No significant acute or chronic clinical toxicities have been observed. © 1987 by Grune & Stratton, Inc.