Regulation of lymphokine-activated killer activity in T-replete and T-cell-depleted human bone marrow by interleukin 4.

Donor-derived lymphokine-activated killer (LAK) cells appear to play a role in mediating an antileukemia effect in recipients of both T-replete and T-cell-depleted (TCD) bone marrow transplants. LAK activity, however, is subject to regulation by cytokines other than interleukin 2 (IL-2). The purpose of this study was to examine the effect of interleukin 4 (IL-4) on the induction of LAK activity in both T-replete and TCD bone marrow. IL-4 inhibited the induction of LAK activity in a time- and dose-dependent manner in both T-replete and TCD bone marrow cultures, although there appeared to be a differential effect, suggesting that T and non-T LAK precursors have different thresholds of sensitivity to IL-4. Single-cell cytotoxicity assays indicated that IL-4 did not inhibit binding of LAK effectors to targets but did reduce the frequency of lytic conjugates. Kinetic analysis techniques demonstrated that IL-4 decreased the maximal rate of target cell lysis by IL-2-activated LAK precursors and inhibited the rate of lytic programming. These data indicate that IL-4 is able to regulate the induction of LAK activity in both T-replete and TCD bone marrow and may play a role in modulating the generation of effector cells with potential antileukemia reactivity in vivo.     

Prevalence of human herpesvirus 6 variant A and B infections in bone marrow transplant recipients as determined by polymerase chain reaction and sequence-specific oligonucleotide probe hybridization.

An oligotyping methodology was devised by using the polymerase chain reaction and sequence-specific oligonucleotide probe hybridization in order to discriminate the A and B variants of human herpesvirus 6 (HHV-6). Comparative DNA sequence analysis of portions of the U1102 (variant A) and Z29 (variant B) genomes revealed polymorphic regions which allowed for the synthesis of variant-specific and consensus oligonucleotide probes. These probes were found to hybridize exclusively to their respective HHV-6 variants. This strategy was then further tested by evaluating 16 clinical isolates derived from patients undergoing bone marrow transplantation to determine the subtype prevalence of HHV-6 infection in these patients. All clinical isolates were documented to be of variant B, indicating that the majority of bone marrow transplantation patients may be preferentially infected with this HHV-6 subtype. This oligotyping strategy may be useful in defining the relative prevalence of HHV-6A and HHV-6B infections in patient populations potentially at risk for HHV-6 disease.     

The vasa vasorum and angioplasty

Interruption of flow in the vasa vasorum may lead to medial necrosis and aneurysm formation. The purpose of this study was to determine whether angioplasty produces significant alterations in the morphology or blood flow of the vasa vasorum of the dilated artery. The morphology of the canine vasa vasorum was studied before and after angioplasty; in a separate experiment vessel wall blood flow (VWBF) in canine carotid arteries was measured after angioplasty to determine whether physiologic regulation of the blood flow was disrupted by arterial dilation. No morphologic changes could be demonstrated in the vasa vasorum of the dilated artery; however, VWBF was increased by 1194 +/- 215% (mean +/- standard error, p less than 0.01) between 90 and 120 minutes after angioplasty. VWBF in the adjacent nondilated arterial segment was also increased (720 +/- 177% between 10-30 minutes, p less than 0.01) but returned toward normal after 60 minutes. Adenosine caused a "paradoxical" decrease in VWBF (p less than 0.05) of the dilated arterial segment while causing increased VWBF (p less than 0.05) in the thoracic aorta. Angioplasty appears to produce persistent hyperemia in the dilated arterial wall. A paradoxical response to adenosine suggests that vasa vasorum in the dilated arterial segment are maximally vasodilated. This may be due to mechanical disruption of vasomotor tone or to release of vasoactive substances.     

Graft-facilitating doses of ex vivo activated gammadelta T cells do not cause lethal murine graft-vs.-host disease.

The purpose of this study was to examine the ability of gamma(delta) T cells to cause graft-vs.-host disease (GVHD) after allogeneic bone marrow transplantation (BMT) and to determine whether these cells offered any therapeutic advantages relative to alphabeta T cells. Due to the paucity of naive gamma(delta) T cells in mice and humans, gamma(delta), T cells (obtained from alpha(beta) T cell-deficient murine donors) were ex vivo activated and expanded in interleukin (IL)-2 so as to achieve sufficient cell numbers and to serve as a more clinically feasible strategy. After transplantation into lethally irradiated hosts, donor gamma(delta) T cells were detected in target organs of GVHD such as the spleen and intestines 2 weeks after BMT and constituted the primary T cell subpopulation. Large doses (150 x 10(6)) of activated gamma(delta) T cells, which we have previously shown capable of facilitating engraftment in MHC-disparate recipients, failed to cause fatal GVHD in lethally irradiated recipients of MHC-incompatible donor marrow grafts (C57BL/6 [H-2b]-->B10.BR [H-2k] and C57BL/6 [H-2b]-B6D2F1[H-2b/d]). The absence of GVHD was confirmed by histologic analysis of target organs, splenic B cell reconstitution, and appropriate negative selection in the thymus, that were all comparable to those observed in mice transplanted with T cell-depleted BM only. While early splenic reconstitution was attributable to donor gamma(delta) T cells, analysis of durably engrafted chimeras 2 months posttransplant revealed that the vast majority of donor splenic T cells expressed the alpha(beta) T cell receptor. The results of secondary adoptive transfer assays showed that these cells were tolerant of recipient alloantigens in vivo, demonstrating that gamma(delta) T cells did not prevent the subsequent development of donor anti-host tolerance in BM-derived alpha(beta) T cells. When comparatively evaluated, the minimal number of naive alpha(beta) T cells necessary for donor engraftment caused significantly more fatal GVHD than the corresponding minimal dose of activated gamma(delta) T cells and thus had a superior therapeutic index. These studies indicate that doses of activated gamma(delta) T cells that are able to promote alloengraftment do not cause lethal GVHD in mice transplanted with MHC-incompatible marrow grafts.     

Peripheral Blood Grafts for T Cell–Replete Haploidentical Transplantation Increase the Incidence and Severity of Cytokine Release Syndrome

T cell–replete post-transplant cyclophosphamide (PTCy)-based protocols have led to increasing use of haploidentical allogeneic hematopoietic cell transplantation (haploHCT). With this approach, bidirectional alloreactivity causing nonengraftment or severe graft-versus-host disease (GVHD) is no a longer major barrier to haploHCT. PTCy eliminates alloreactive lymphocytes but spares CD34⁺ stem cells and regulatory T lymphocytes, resulting in reliable hematopoietic recovery with relatively low incidence of GVHD. The immediate post-haploHCT course, usually before PTCy administration, is often complicated by cytokine release syndrome (CRS). The predictors of CRS and its effect on outcomes post-transplant have not been fully ascertained. We analyzed the outcomes of 66 patients who received haploHCT at our institution. Using published CRS criteria we identified 48 patients who developed CRS. In multivariate analysis peripheral blood grafts were significantly associated with grade ≥ 2 CRS, compared with bone marrow. Grade ≥ 2 CRS (compared with grade < 2) was not associated with differences in overall survival or nonrelapse mortality. Severe CRS was associated with a statistically nonsignificant trend toward higher incidences of grades III to IV acute GVHD, especially in the context of peripheral blood grafts. CRS is a common complication after T cell–replete peripheral blood haploHCT, but post-transplant survival outcomes may not be affected in those with severe CRS.