Differential CD26-mediated activation of the CD3 and CD2 pathways after CD6-depleted allogeneic bone marrow transplantation

Patients who have undergone allogeneic bone marrow transplantation (allo-BMT) are susceptible to a variety of opportunistic infectious complications in the months to years after engraftment. Impaired in vitro T-cell functions have been documented in these patients, and these T-cell dysfunctions contribute to the prolonged immune deficiency after allo-BMT. In the present study, we examined the expression of CD26 as well as the reconstitution of CD26-mediated T-cell costimulation via the CD3 and CD2 pathways at various times in patients aged greater than 18 years after CD6-positive, T-cell depleted allo- BMT. We found that the percentage of CD26- and CD3-positive cells, as well as the levels of expression of both antigens, was lower than in normal controls during the first 4 months after CD6-depleted allo-BMT. Subsequently, the amount of lymphocytes expressing CD3 and CD26 and the quantitative surface expression of CD3 and CD26 were not significantly different in patients and normal controls. Functional studies showed that CD26-mediated T-cell proliferation via the CD3 pathway was considerably improved and almost reached normal levels by 1 year, whereas recovery of CD26-mediated T-cell proliferation via the CD2 pathway was delayed for at least 2 years after CD6-depleted allo-BMT. As CD26 involvement in the regulation of human thymocyte activation is restricted preferentially to the CD3 pathway--unlike its involvement with both CD3 and CD2 pathways of peripheral T cells--our results suggest that the different effects of CD26-mediated costimulation via the CD3 and CD2 pathways after CD6-depleted allo-BMT may be a reflection of peripheral T-cell immaturity in those individuals, similar to that seen in mature medullary thymocytes or cord T lymphocytes.     

The development of cellular immunity to Epstein-Barr virus after allogeneic bone marrow transplantation

Epstein-Barr virus-induced lymphoproliferative disease (EBV-LPD) is a potentially lethal complication during the first 6 months after allogeneic bone marrow transplantation (BMT). To determine whether deficiencies of EBV-specific cellular immunity contribute to EBV-LPD susceptibility and distinguish patients at risk, we performed limiting dilution analysis to quantify anti-EBV cytotoxic T-lymphocyte precursor (CTLp) frequencies in 26 recipients of unmodified or T-cell-depleted (TCD) grafts from EBV-seropositive donors. At 3 months post-BMT (n = 26), only five patients had EBV CTLp frequencies in the range of seropositive normal controls, irrespective of the type of transplant administered. By 6 months post-BMT, 9 of 13 patients tested had EBV CTLp frequencies within the normal range. The time period in which these patients had deficient cellular immunity to EBV corresponds to the period in which we have observed EBV-LPD in most prior patients. One patient with a low EBV CTLp frequency at 4 months post-BMT developed an EBV-LPD. Within 2 weeks of receiving an infusion of donor peripheral blood mononuclear cells (PBMC) providing less than 1,200 EBV- specific cytotoxic T-cell precursors, populations of EBV-specific CTL in the circulation were restored to levels detected in normal seropositive adults. Concurrently, the patient achieved a regression of the EBV-LPD, which has been sustained without further therapy. These studies indicate that recipients of both unmodified and TCD marrow grafts have profound deficiencies of EBV-specific T cell-mediated immunity early posttransplant, and that the period of risk for EBV-LPD closely corresponds to this interval of severe deficiency. Treatment of one patient with EBV-LPD with marrow donor-derived PBMC induced a rapid expansion of EBV-specific cytotoxic T-cell populations that occurred contemporaneously with the clinical regression of disease.     

Assessment of aldehyde dehydrogenase in viable cells

Cytosolic aldehyde dehydrogenase (ALDH), an enzyme responsible for oxidizing intracellular aldehydes, has an important role in ethanol, vitamin A, and cyclophosphamide metabolism. High expression of this enzyme in primitive stem cells from multiple tissues, including bone marrow and intestine, appears to be an important mechanism by which these cells are resistant to cyclophosphamide. However, although hematopoietic stem cells (HSC) express high levels of cytosolic ALDH, isolating viable HSC by their ALDH expression has not been possible because ALDH is an intracellular protein. We found that a fluorescent aldehyde, dansyl aminoacetaldehyde (DAAA), could be used in flow cytometry experiments to isolate viable mouse and human cells based on their ALDH content. The level of dansyl fluorescence exhibited by cells after incubation with DAAA paralleled cytosolic ALDH levels determined by Western blotting and the sensitivity of the cells to cyclophosphamide. Moreover, DAAA appeared to be a more sensitive means of assessing cytosolic ALDH levels than Western blotting. Bone marrow progenitors treated with DAAA proliferated normally. Furthermore, marrow cells expressing high levels of dansyl fluorescence after incubation with DAAA were enriched for hematopoietic progenitors. The ability to isolate viable cells that express high levels of cytosolic ALDH could be an important component of methodology for identifying and purifying HSC and for studying cyclophosphamide-resistant tumor cell populations.     

Quantification of dispersion of Gd-DTPA from the initial area of enhancement into the peritumoral zone of edema in brain tumors

To evaluate Gd-DTPA contrast enhancement of brain tumors over time and to describe the dispersion of contrast into the zone of peritumoral edema. We performed MR imaging with a dose of 0.4 mmol Gd-DTPA/kg on eleven patients diagnosed with 5 different supratentorial tumors. MR imaging was done at five intervals between 5 min and 6 h. The change in zone of enhancement was measured for each time point, and a linear measurement was made of the furthest dispersion of contrast from the original volume of enhancement. An increase in the zone of enhancement over time was seen for all tumors; the average increase in volume of contrast was 14.76 ± 3.35 cm³ (mean ± standard deviation). The largest changes in the zone of contrast enhancement, 18.6 ± 4.63 cm³, were seen in glioblastoma multiforme. The expansion of contrast enhancement assumed the morphology of the surrounding edema. The dispersion of Gd-DTPA over time into the zone of peritumoral edema is a potential source of error in clinical settings when there is a delay between Gd-DTPA injection and scanning.     

Clinical trial of imipenem/cilastatin in severely burned and infected patients

Imipenem/cilastatin was examined for safety and efficacy in a population of 20 seriously burned patients with acute bacterial infections. The study was made up of 18 males and two females with an average age of 38 years and average burn size of 52 per cent of the total body surface area. Inhalation injury was present in 14 patients. The infections treated included 16 pulmonary, two urinary tract, one wound and one bacteremia. Treatment was clinically successful in 13 patients; five patients had no improvement and the clinical response could not be determined in two in whom multisystem organ failure preceded the treated infection. All of the clinical failures were in the pulmonary infection group. No serious toxicity or side effects were noted. No patient died while receiving the drug or as a consequence of known failure of the drug. Microbiologic success was noted in 12. Resistant organisms developed in eight of whom five were in the clinical failure group. Pseudomonas aeruginosa resistant to imipenem/cilastatin was isolated from seven patients and occurred at an average of 3.6 days after treatment was begun.     

The regulation and consequences of immune-mediated cell death in atheromatous diseases

Atheromatous diseases are lipid and cell-rich vascular disorders that include coronary artery disease (CAD), transplant vascular disease (TVD), and restenosis. Considering the inflammatory nature of these diseases, cytotoxic immune mechanisms such as the FasL and granzyme/perforin pathways most likely play important roles in the development and remodeling of many lesions. Furthermore, although the contributions of immune responses to each disease vary, the correspondent localization of certain mediators and effectors suggests that they may contribute to a spectrum of atheromatous diseases. In this review, the contribution of immune cell-mediated cell death in the onset and pathogenesis of CAD and TVD is examined.