Allografts stimulate cross-reactive virus-specific memory CD8 T cells with private specificity.

Viral infections have been associated with the rejection of transplanted allografts in humans and mice, and the induction of tolerance to allogeneic tissues in mice is abrogated by an ongoing viral infection and inhibited in virus-immune mice. One proposed mechanism for this 'heterologous immunity' is the induction of alloreactive T cell responses that cross-react with virus-derived antigens. These cross-reactive CD8 T cells are generated during acute viral infection and survive into memory, but their ability to partake in the immune response to allografts in vivo is not known. We show here that cross-reactive, virus-specific memory CD8 T cells from mice infected with LCMV proliferated in response to allografts. CD8 T cells specific to several LCMV epitopes proliferated in response to alloantigens, with the magnitude and hierarchy of epitope-specific responses varying with the private specificities of the host memory T cell repertoire, as shown by adoptive transfer studies. Last, we show that purified LCMV-specific CD8 T cells rejected skin allografts in SCID mice. These findings therefore implicate a potential role for heterologous immunity in virus-induced allograft rejection.

Murine cytomegalovirus is regulated by a discrete subset of natural killer cells reactive with monoclonal antibody to Ly49H.

Antiviral roles of natural killer (NK) cell subsets were examined in C57BL/6 mice infected with murine cytomegalovirus (MCMV) and other viruses, including lymphocytic choriomeningitis virus (LCMV), vaccinia virus (VV), and mouse hepatitis virus (MHV). Each virus vigorously induced an NK cell infiltrate into the peritoneal cavity and liver, causing some redistributions of NK cell subsets defined by monoclonal antibody (mAb) directed against Ly49A, C/I, D, and G2. Striking results were seen with a mAb (1F8) reactive with the positively signaling molecule Ly49H, present in MCMV-resistant C57BL/6 mice. mAb 1F8 also stains Ly49 C and I, but exclusion of those reactivities with mAb 5E6, which recognizes Ly49 C and I, indicated that Ly49H(+) cells infiltrated the peritoneal cavity and liver and were particularly effective at synthesizing interferon gamma. Depletion of 1F8(+) but not 5E6(+) cells in vivo by mAb injections enhanced MCMV titers by 20-1,000-fold in the spleen and approximately fivefold in the liver. Titers of LCMV or VV were not enhanced. These anti-MCMV effects were attributed to prototypical NK1.1(+)CD3(-) NK cells and not to NK1.1(+)CD3(+) "NK/T" cells. This is the first evidence that control of a virus infection in vivo is mediated by a distinct NK cell subset.

Direct versus indirect tests of memory: directed forgetting meets the generation effect.

Subjects read 20 words and generated 20 others from definitions during a 40-item study phase. Production of each word was followed by an instruction to remember or to forget that word. In free recall, a direct test of memory, words that had been generated were recalled much better than words that had been read. The remember-forget instructional manipulation affected read words but not generated words. In speeded word reading, an indirect test of memory, all studied words showed priming, but read words showed more priming than generated words. Here, the effect of remember versus forget instructions appeared only for generated words. These dissociations of a direct and an indirect test indicate that two powerful encoding manipulations affect separable processes to which these tests are differentially sensitive.

Bystander sensitization to activation-induced cell death as a mechanism of virus-induced immune suppression.

Viral infections which induce strong T-cell responses are often characterized by a period of transient immunodeficiency associated with the failure of host T cells to proliferate in response to mitogens or to mount memory recall responses to other antigens. During acute infections, most of the activated, proliferating virus-specific T cells are sensitized to undergo apoptosis on strong T-cell receptor (TCR) stimulation, but it has not been known why memory T cells not specific for the virus fail to proliferate on exposure to their cognate antigen. Using a lymphocytic choriomeningitis virus (LCMV) infection model in which LCMV-immune Thy 1.1(+) splenocytes are adoptively transferred into Thy 1.2(+) LCMV carrier mice, we demonstrate here that T cells clearly defined as not specific for the virus are sensitized to undergo activation-induced cell death on TCR stimulation in vitro. This bystander sensitization was in part dependent on the expression of Fas ligand (FasL) on the activated virus-specific cells and gamma interferon (IFN-gamma) receptor expression on the bystander T cells. We propose that FasL from highly activated antiviral T cells may sensitize IFN-gamma-conditioned T cells not specific for the virus to undergo apoptosis rather than to proliferate on encountering antigen. This may in part explain the failure of memory T cells to respond to recall antigens during acute and persistent viral infections.

Virus-induced abrogation of transplantation tolerance induced by donor-specific transfusion and anti-CD154 antibody.

Treatment with a 2-week course of anti-CD154 antibody and a single transfusion of donor leukocytes (a donor-specific transfusion or DST) permits skin allografts to survive for >100 days in thymectomized mice. As clinical trials of this methodology in humans are contemplated, concern has been expressed that viral infection of graft recipients may disrupt tolerance to the allograft. We report that acute infection with lymphocytic choriomeningitis virus (LCMV) induced allograft rejection in mice treated with DST and anti-CD154 antibody if inoculated shortly after transplantation. Isografts resisted LCMV-induced rejection, and the interferon-inducing agent polyinosinic:polycytidylic acid did not induce allograft rejection, suggesting that the effect of LCMV is not simply a consequence of nonspecific inflammation. Administration of anti-CD8 antibody to engrafted mice delayed LCMV-induced allograft rejection. Pichinde virus also induced acute allograft rejection, but murine cytomegalovirus and vaccinia virus (VV) did not. Injection of LCMV approximately 50 days after tolerance induction and transplantation had minimal effect on subsequent allograft survival. Treatment with DST and anti-CD154 antibody did not interfere with clearance of LCMV, but a normally nonlethal high dose of VV during tolerance induction and transplantation killed graft recipients. We conclude that DST and anti-CD154 antibody induce a tolerant state that can be broken shortly after transplantation by certain viral infections. Clinical application of transplantation tolerance protocols may require patient isolation to facilitate the procedure and to protect recipients.

Conscious and unconscious processing of nonverbal predictability in Wernicke's area.

The association of nonverbal predictability and brain activation was examined using functional magnetic resonance imaging in humans. Participants regarded four squares displayed horizontally across a screen and counted the incidence of a particular color. A repeating spatial sequence with varying levels of predictability was embedded within a random color presentation. Both Wernicke's area and its right homolog displayed a negative correlation with temporal predictability, and this effect was independent of individuals' conscious awareness of the sequence. When individuals were made aware of the underlying sequential predictability, a widespread network of cortical regions displayed activity that correlated with the predictability. Conscious processing of predictability resulted in a positive correlation to activity in right prefrontal cortex but a negative correlation in posterior parietal cortex. These results suggest that conscious processing of predictability invokes a large-scale cortical network, but independently of awareness, Wernicke's area processes predictive events in time and may not be exclusively associated with language.

Autologous stem cell transplantation for refractory and relapsed Hodgkin's disease: factors predictive of prolonged survival.

We analyzed patient, disease, and treatment related factors associated with long-term disease-free survival (DFS) in 62 patients with refractory or recurrent Hodgkin's disease treated with high-dose cyclophosphamide (6000 mg/m2), carmustine (BCNU; 300 mg/m2), and etoposide (900 mg/m2) (CBV) followed by autologous stem cell transplantation. There were no deaths resulting from toxicity of the preparative regimen, and all patients survived the peritransplant period. At 28 days post-transplant, the complete response (CR) rate was 76%. Patients who achieved a CR had a 50% estimated 3-year DFS (95% CI, 35-64%). Twenty-three (37%) patients remain in continuous clinical remission 1.3 to 7.7 years (median 3.8 years) after transplantation. In a univariate analysis, factors significantly associated with improved DFS included absence of B symptoms (fever, night sweats and unexplained weight loss) at transplant, response to pre-transplant salvage chemotherapy, less tumor bulk at time of transplant, and fewer prior treatment regimens. Stepwise multivariate analysis showed that the absence of B symptoms at time of transplant was independently and significantly associated with improved DFS after transplantation. CBV with autologous stem cell support can produce durable remissions with acceptable toxicity in a substantial proportion of patients who are asymptomatic at time of transplant. Earlier application of transplantation or development of additional effective antineoplastic modalities will be required to improve the results of transplantation for patients with advanced Hodgkin's disease.

Randomized comparison of cyclophosphamide-total body irradiation versus busulfan-cyclophosphamide conditioning in autologous bone marrow transplantation for acute myeloid leukemia.

PURPOSE: This prospective trial of autologous bone marrow transplantation for acute myeloid leukemia was undertaken to compare the outcome using two different preparative regimens. METHODS AND MATERIALS: Between October 1987 and April 1993, 35 patients with acute myeloid leukemia in first (n = 12) or greater (n = 23) remission were stratified by remission status and randomized to undergo 4-hydroperoxycyclophosphamide purged autologous bone marrow transplantation after either cyclophosphamide (120 mg/kg) and total body irradiation (1320 Gy in eight fractions over 4 days) (CY/TBI), or busulfan (16 mg/kg) and cyclophosphamide (200 mg/kg) (BU/CY) conditioning. RESULTS: At 2 years, overall survival and disease-free survival were 39% (95% confidence intervals (CI) 22-57%) and 36% (95% CI 19-52%), respectively. Patients in first complete remission had a significantly better outcome with a 2-year disease free survival of 57% (95% CI 28-86%) compared to others at 24% (95% CI 6-43%, log rank p = 0.048). For patients conditioned with CY/TBI, the estimated 2-year disease-free survival was 50% compared to 24% for patients conditioned with BU/CY (log rank p = 0.12). Estimated 2-year relapse rates were 43% vs. 70% (log rank p = 0.17), respectively. For patients in first complete remission no differences in disease-free survival (2-year estimates 67% vs. 50%, log rank p = 0.69), between the two regimens were observed. For patients in greater than first complete remission there was a trend towards improved disease-free survival in the CY/TBI arm (2-year estimates 42% vs. 9%, log rank p = 0.06). There were no differences in time to white blood cell count (WBC) engraftment, absolute neutrophil count of > 500, incidence of bacteremias, or median time to hospital discharge between the two regimens. Acute toxicities were similar. Interstitial pneumonitis developed in two patients (one on each arm), while veno occlusive disease developed in three BU/CY patients, but none of the CY/TBI patients (log rank p = 0.07). CONCLUSIONS: Cyclophosphamide-total body irradiation provided an equivalent or better outcome to BU/CY, particularly in advanced patients, and should remain the standard by which new regimens are judged. The high relapse rate with both regimens, especially patients who were in greater than in first complete remission, emphasizes the need for early transplant and for new strategies to improve outcome.

Diuretics, serum potassium and ventricular arrhythmias in the Multiple Risk Factor Intervention Trial.

To examine the relation between diuretic use and ventricular premature complexes (VPCs) in the Multiple Risk Factor Intervention Trial, data derived from the baseline and annual rest electrocardiograms were analyzed for men in the special-intervention (SI) and usual-care (UC) groups. At baseline, age, diuretic use and presence of other rest electrocardiographic abnormalities were significantly associated with the prevalence of VPCs. Among diuretic users at baseline, those with lower serum potassium levels were most likely to have VPCs. Over the follow-up period among nonhypertensive persons the relative risk (SI/UC) for the occurrence of VPCs during follow-up was 0.83, and for hypertensives this relative risk increased linearly from 1.08 to 1.42, with higher levels of diastolic blood pressure at entry (p less than 0.01 for linear trend of relative risk estimates). This was due to an increasing risk among the SI group, and the risk was independent of the presence or absence of rest electrocardiographic abnormalities at baseline. The relative risk estimate, diuretic vs no diuretic, for development of VPCs was approximately 1.2 (p = 0.04) for SI men and 1.1 (p = 0.35) for UC men. The reduction in serum potassium level was greater for those with VPCs, and regression analysis showed that low serum potassium levels were significantly associated with the incidence of VPCs in both study groups. These data confirm and quantify the relation between diuretic drugs and VPCs and suggest that at least 1 mechanism of diuretic-induced VPCs is potassium depletion.