RESUMO
Para-Bombay is a rare phenotype with a homozygous nonfunctional FUT1 gene and a normal FUT2 gene leading to H-deficient red blood cells (RBCs) with or without ABH substances, depending on inheritance of the ABO gene. This case is about a 5-day-old male baby suffering from sepsis who required a 45-mL packed RBC transfusion. The baby's sample tested as A1B, D+ and mother's sample tested as group O, D+ with group 4 discrepancy due to ABO isoagglutinins. Further workup of the mother's sample with anti-H lectin was negative, which suggested the mother to be group Oh, D+. Antibody screening was panreactive with negative autocontrol, suggestive of anti-H. The titer of immunoglobulin (Ig)M anti-H was 64, IgG titer using dithiothreitol was 8, and anti-IH was absent. A negative adsorption and elution test suggested that RBCs were devoid of A and B antigens. The father's sample tested clearly as group A1, D+; hence, the cis-AB blood group was ruled out in the baby. The secretor study of the mother's saliva revealed the presence of B and H substances that neutralized polyclonal B and H antisera. Therefore, we concluded that the mother was of the para-Bombay (Bh) phenotype. This case highlights the importance of reverse grouping and resolving blood grouping discrepancies between mother and child-in this case because of an incongruous ABO blood type of the baby and the mother who was previously tested as group O, D+.Para-Bombay is a rare phenotype with a homozygous nonfunctional FUT1 gene and a normal FUT2 gene leading to H-deficient red blood cells (RBCs) with or without ABH substances, depending on inheritance of the ABO gene. This case is about a 5-day-old male baby suffering from sepsis who required a 45-mL packed RBC transfusion. The baby's sample tested as A1B, D+ and mother's sample tested as group O, D+ with group 4 discrepancy due to ABO isoagglutinins. Further workup of the mother's sample with anti-H lectin was negative, which suggested the mother to be group Oh, D+. Antibody screening was panreactive with negative autocontrol, suggestive of anti-H. The titer of immunoglobulin (Ig)M anti-H was 64, IgG titer using dithiothreitol was 8, and anti-IH was absent. A negative adsorption and elution test suggested that RBCs were devoid of A and B antigens. The father's sample tested clearly as group A1, D+; hence, the cis-AB blood group was ruled out in the baby. The secretor study of the mother's saliva revealed the presence of B and H substances that neutralized polyclonal B and H antisera. Therefore, we concluded that the mother was of the para-Bombay (Bh) phenotype. This case highlights the importance of reverse grouping and resolving blood grouping discrepancies between mother and childin this case because of an incongruous ABO blood type of the baby and the mother who was previously tested as group O, D+.
Assuntos
Sistema ABO de Grupos Sanguíneos , Mães , Tipagem e Reações Cruzadas Sanguíneas , Criança , Eritrócitos , Feminino , Humanos , Recém-Nascido , Masculino , FenótipoRESUMO
This article presents a summary of incident management guidelines for traumatically injured teeth during orthodontic treatment. In addition, treatment of a 17-year-old patient with traumatic extrusion and palatal displacement of the permanent maxillary incisors while undergoing active orthodontic treatment is reported.
Assuntos
Incisivo/lesões , Avulsão Dentária/terapia , Técnicas de Movimentação Dentária/métodos , Adolescente , Ciclismo/lesões , Protocolos Clínicos , Tomografia Computadorizada de Feixe Cônico/métodos , Seguimentos , Humanos , Masculino , Contenções Ortodônticas , Fios Ortodônticos , Radiografia Interproximal/métodos , Mobilidade Dentária/terapiaRESUMO
BACKGROUND: Blood donors with high Hb are often deferred for the presumed risk of polycythemia vera (PV). However, adequate data to substantiate or refute this hypothesis is lacking. METHODOLOGY: We conducted an observational study on blood donors found to have high hemoglobin (Hb≥18g/dL) during the pre-donation screening process using a portable hemoglobinometer at our blood center for four months. We adopted a cost effective methodology wherein a questionnaire was used to elicit the secondary causative factors of high hemoglobin and a complete blood count test to observe the blood cell parameters and JAK2V617F mutation test was performed in a subset of donors lacking secondary erythrocytosis (SE) history. RESULTS: Of the total 7076 donors enrolled, 112 male donors (1.58%) had high hemoglobin. The majority (70.4%) were repeat donors with mean age of 31.4 years. About 61% of the donors had attributable factors for SE like smoking, occupational exposure to carbon monoxide. The mean hemoglobin value of capillary and venous hemoglobin demonstrated a statistically significant difference (P<0.05) where 2.7% of donors had venous Hb<18g/dL. The hematological profile of all the donors showed increased RBC but normal platelet and WBC count. Of 24 donors included for the JAK2V617F test, none had a positive report. CONCLUSION: This study suggests high hemoglobin in blood donors is less likely due to PV. Hence, re-considering their deferral may help alleviate donor anxiety and allow donor return. However, multi-centric studies are required to develop consensus statements on PV risk status and blood donation eligibility.
Assuntos
Doenças Hematológicas , Neoplasias , Adulto , Doadores de Sangue , Feminino , Hemoglobina Falciforme , Hemoglobinas/análise , Humanos , Índia/epidemiologia , MasculinoRESUMO
BACKGROUND: Transfusion transmissible syphilis is caused by Treponema pallidum; blood donors are traditionally screened with non-treponemal antibody tests to ensure transfusion safety. Detection of specific antibodies against T. pallidum is employed in reverse algorithm screening. We aim to analyze the utility of the reverse algorithm screening strategy for T. pallidum and to determine the prevalence trends among blood donors in our centre. MATERIAL AND METHODS: The study was conducted in a Transfusion Centre catering to the 2030 bedded Tertiary Care Centre in coastal Karnataka in two timelines from 2012 to 2014, and 2019 to 2020, respectively. A fully automated Enzyme-Linked Immunosorbent Assay and Enhanced Chemiluminescence Immunoassay, which detect both IgM and IgG antibodies against T.pallidum were used in the study. Blood donor data from 2008 to 2020 were also analyzed to observe the trend in prevalence rate of syphilis among blood donors. RESULTS: Among 26329 and 388 blood donors screened with ELISA and ECI, 134 (0.51%) and 9 (2.3%) were reactive to T. pallidum antibodies respectively. TPHA confirmed that 104 and 9 donors were reactive from each of the ELISA and ECI reactive donor groups. The increase in the prevalence of syphilis was observed with the use of reverse algorithm compared to the traditional strategy. The prevalence of syphilis in the present study ranged from 0.02 to 0.28%. CONCLUSION: The reverse algorithm screening can give a better result with a positive predictive value of 77.61% and 88.9% for ELISA and ECI. respectively Our study found that the use of reverse algorithm might increase the blood discard rate slightly but adds on to safety of blood components.
Assuntos
Sífilis , Algoritmos , Anticorpos Antibacterianos , Doadores de Sangue , Humanos , Índia/epidemiologia , Prevalência , Sífilis/diagnóstico , Sífilis/epidemiologia , Sorodiagnóstico da SífilisRESUMO
The present study investigated the chemical composition of precipitation at Comba, Madgaon, South Goa during southwest monsoon. The rainwater samples were collected on event basis during June-September 2008 and were analyzed for pH, major anions F, Cl, NO(3), SO(4)) and cations (Ca, Mg, Na, K, NH(4)). The pH value varied from 5.36 to 6.91 (6.25 +/- 0.28) indicating alkaline nature of rainwater and dominance of Cl and Na in precipitation. The Neutralization factors (NF) was found to be NFCa = 1.22, NFMg = 0.42, NFNH(4) = 0.37 and NFK = 0.14 indicating below cloud process in which crustal components are responsible for neutralization of anions.
Assuntos
Cátions/química , Monitoramento Ambiental , Chuva/química , Amônia , Ânions/análise , Ânions/química , Cálcio , Cloretos , Fluoretos , Geografia , Concentração de Íons de Hidrogênio , Índia , Magnésio , Nitratos , Oceanos e Mares , Potássio , Estações do Ano , Sódio , SulfatosRESUMO
BACKGROUND: While yoga is thought to reduce the risk of chronic non-communicable diseases such as diabetes, there are no studies on insulin sensitivity in long term practitioners of yoga. We assessed insulin sensitivity and cardiac autonomic function in long term practitioners of yoga. METHODS: Fifteen healthy, young, male practitioners of yoga were compared with 15 young, healthy males who did not practice yoga matched for body-mass index. Fasting insulin sensitivity was measured in the fasting state by the hyperinsulinaemic-euglycaemic clamp. RESULTS: There were no significant differences between the groups in their anthropometry or body composition. However, the fasting plasma insulin was significantly lower in the yoga group. The yoga group was also more insulin sensitive (yoga 7.82 [2.29] v. control 4.86 [11.97] (mg/[kg.min])/(microU/ml), p < 0.001). While the body weight and waist circumference were negatively correlated with glucose disposal rate in the controls, there were no similar correlations in the yoga group. The yoga group had significantly higher low-frequency power and lower normalized high-frequency power. CONCLUSION: Long term yoga practice (for 1 year or more) is associated with increased insulin sensitivity and attenuates the negative relationship between body weight or waist circumference and insulin sensitivity.
Assuntos
Sistema Nervoso Autônomo , Coração , Resistência à Insulina , Insulina/sangue , Yoga , Adulto , Análise de Variância , Índice de Massa Corporal , Estudos de Casos e Controles , Estudos Transversais , Jejum , Técnica Clamp de Glucose , Humanos , MasculinoRESUMO
Previous studies have found that female rats are less sensitive than males to hypothalamic-pituitary-adrenal axis feedback inhibition by exogenous glucocorticoid administration. To determine whether estrogen contributes to this sex difference, we examined the effects of the estrogen antagonists tamoxifen and C1628 on the ACTH and corticosterone responses to restraint stress. CI628 increased both the ACTH and corticosterone response to restraint stress, and tamoxifen increased the ACTH response to restraint. Using overiectomized female rats, we also examined the effects of seven days of estradiol and/or progesterone replacement. Low dose estradiol decreased the ACTH but not the corticosterone response to restraint stress while progesterone had no effect on ACTH or corticosterone responses. The combination of estradiol and progesterone also decreased the ACTH response to stress, and the magnitude of the effect did not differ from that found with estradiol treatment alone. These data suggest that in the physiological range estradiol is an important inhibitory factor in the hypothalamic-pituitary-adrenal stress response of females.
Assuntos
Hormônio Adrenocorticotrópico/metabolismo , Antagonistas de Estrogênios/farmacologia , Estrogênios/agonistas , Estresse Psicológico/metabolismo , Animais , Anti-Inflamatórios/administração & dosagem , Anti-Inflamatórios/farmacologia , Corticosterona/administração & dosagem , Corticosterona/farmacologia , Implantes de Medicamento/administração & dosagem , Implantes de Medicamento/farmacologia , Estradiol/farmacologia , Retroalimentação/efeitos dos fármacos , Feminino , Glucocorticoides/antagonistas & inibidores , Sistema Hipotálamo-Hipofisário/efeitos dos fármacos , Masculino , Nitromifeno/farmacologia , Ovariectomia , Progesterona/farmacologia , Ratos , Ratos Sprague-Dawley , Restrição Física , Tamoxifeno/farmacologiaRESUMO
BACKGROUND: Liver transplants in the rat strain combination PVG-to-Dark Agouti are spontaneously tolerated, whereas kidney transplants in the same strain combination are rejected in 7-9 days. METHODS: To identify organ-specific differences that might yield further information about the mechanism of tolerance induction in this strain combination, liver or kidney grafts, spleen, and draining lymph nodes were harvested at days 1, 3, 5, and 7, and examined by immunohistochemistry, terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay, and reverse transcriptase-polymerase chain reaction for interferon-gamma, interleukin (IL)-2, IL-4, and IL-10. RESULTS: Renal allograft rejection was associated with the progressive development of an intense mononuclear cell infiltrate. Markers of lymphocyte activation and cytokine up-regulation appeared from day 3, and many apoptotic parenchymal cells were noted on days 5-7, at the peak of rejection. Conversely, liver allograft tolerance was associated with more rapid infiltration by activated T cells and earlier increases in cytokine expression, but with a more limited degree of cellular infiltration. Concurrent with the early activation, high levels of apoptosis were found in areas of leukocyte infiltrate, paralleling the disappearance of activated T cells from the graft between days 3 and 5. CONCLUSIONS: Apoptosis of infiltrating leukocytes in liver allografts may represent an important process in the induction of spontaneous liver transplant tolerance and may underlie the abortive nature of the effector response observed within tolerated livers. In contrast, activated cells in renal allografts in the same strain combination survive and proliferate, express high levels of cytokines, and are efficient in bringing about graft destruction.
Assuntos
Citocinas/metabolismo , Rejeição de Enxerto/metabolismo , Sobrevivência de Enxerto/fisiologia , Transplante de Rim , Rim/metabolismo , Transplante de Fígado , Animais , Apoptose/fisiologia , Movimento Celular/fisiologia , Citocinas/genética , Rejeição de Enxerto/patologia , Rejeição de Enxerto/fisiopatologia , Rim/patologia , Rim/fisiopatologia , Cinética , Leucócitos/patologia , Leucócitos/fisiologia , Fígado/patologia , Fígado/fisiopatologia , Reação em Cadeia da Polimerase , RNA Mensageiro/metabolismo , Ratos , Ratos Endogâmicos , Transcrição Gênica , Transplante HomólogoRESUMO
We sought to examine further the potential role of nitric oxide (NO) in the neurally mediated cutaneous vasodilation in nonacral skin during body heating in humans. Six subjects were heated with a water-perfused suit while cutaneous blood flow was measured by using laser-Doppler flowmeters placed on both forearms. The NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) was given selectively to one forearm via a brachial artery catheter after marked cutaneous vasodilation had been established. During body heating, oral temperature increased by 1.1 +/- 0.1 degreesC while heart rate increased by 30 +/- 6 beats/min. Mean arterial pressure stayed constant at 84 +/- 2 mmHg. In the experimental forearm, cutaneous vascular conductance (CVC; laser-Doppler) decreased to 86 +/- 5% of the peak response to heating (P < 0.05 vs. pre-L-NMMA values) after L-NMMA infusion. In some subjects, L-NMMA caused CVC to fall by approximately 30%; in others, it had little impact on the cutaneous circulation. CVC in the control arm showed a similar increase with heating, then stayed constant while L-NMMA was given to the contralateral side. These results demonstrate that NO contributes modestly, but not consistently, to cutaneous vasodilation during body heating in humans. They also indicate that NO is not the only factor responsible for the dilation.
Assuntos
Inibidores Enzimáticos/farmacologia , Temperatura Alta/efeitos adversos , Óxido Nítrico Sintase/antagonistas & inibidores , Pele/irrigação sanguínea , Vasodilatação/efeitos dos fármacos , ômega-N-Metilarginina/farmacologia , Adulto , Inibidores Enzimáticos/administração & dosagem , Feminino , Antebraço/irrigação sanguínea , Humanos , Infusões Intravenosas , Fluxometria por Laser-Doppler , Masculino , Fluxo Sanguíneo Regional/efeitos dos fármacos , Sudorese/efeitos dos fármacos , Sudorese/fisiologia , ômega-N-Metilarginina/administração & dosagemRESUMO
We sought to investigate further the roles of sweating, ACh spillover, and nitric oxide (NO) in the neurally mediated cutaneous vasodilation during body heating in humans. Six subjects were heated with a water-perfused suit while cutaneous blood flow was measured with a laser-Doppler flowmeter. After a rise in core temperature (1. 0 +/- 0.1 degrees C) and the establishment of cutaneous vasodilation, atropine and subsequently the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) were given to the forearm via a brachial artery catheter. After atropine infusion, cutaneous vascular conductance (CVC) remained constant in five of six subjects, whereas L-NAME administration blunted the rise in CVC in three of six subjects. A subsequent set of studies using intradermal microdialysis probes to selectively deliver drugs into forearm skin confirmed that atropine did not affect CVC. However, perfusion of L-NAME resulted in a significant decrease in CVC (37 +/- 4%, P < 0.05). The results indicate that neither sweating nor NO release via muscarinic receptor activation is essential to sustain cutaneous dilation during heating in humans.
Assuntos
Atropina/farmacologia , Temperatura Corporal/fisiologia , NG-Nitroarginina Metil Éster/farmacologia , Pele/irrigação sanguínea , Adulto , Artéria Braquial/efeitos dos fármacos , Artéria Braquial/fisiologia , Inibidores Enzimáticos/farmacologia , Feminino , Humanos , Recém-Nascido , Bombas de Infusão , Masculino , Microdiálise , Parassimpatolíticos/farmacologia , Fluxo Sanguíneo Regional/efeitos dos fármacos , Fenômenos Fisiológicos da Pele/efeitos dos fármacos , Sudorese/fisiologia , Fatores de Tempo , Resistência Vascular/efeitos dos fármacosRESUMO
BACKGROUND: Transfusion-associated hepatitis B viral infection continues to be a major problem in India even after adoption of mandatory screening for HBsAg by ELISA method. The high incidence of TAHBV is reported in patients receiving multiple transfusions. OBJECTIVE: To study the seroprevalence of hepatitis B core antibody among healthy voluntary blood donors SUBJECTS AND METHODS: The study was conducted in the department of Transfusion Medicine of a tertiary care referral hospital. A total of 12,232 volunteers after passing through the stringent criteria were selected for blood donation. Donor samples were tested for all mandatory transfusion transmissible infections and anti HBc IgM (Monolisa HBc IgM PLUS:BIO-RAD, France). Reactive results were confirmed by repeat testing in duplicate. Donor data was analyzed using SPSS software and Chi-square test was used to calculate the significance of difference between the groups. RESULTS: A total of 12,232 healthy voluntary blood donors were recruited. Majority (93.4%) were males. Median age of donor population was 26 years (range: 18-60 years). Eighty six (0.7%) were positive for HBsAg, which comes under "low prevalence (<2%) zone" as per WHO. On screening for HBcAg Ig M, 15 (0.1%) were found to be positive and none were HBsAg reactive. There was no significance of difference in the mean age between reactive and non-reactive donors. CONCLUSION: Evaluating the usefulness of anti-HBc screening is critical. Anti HBcAg IgM screening may be included in routine screening of donors as it is an indicator of occult HBV during window period. The cost and the unnecessary wastage of the blood units when they are positive for anti HBsAg along with the core antibody need to be studied.
RESUMO
Hyperhomocysteinemia is prevalent among patients with chronic kidney disease (CKD) and has been linked to progressive kidney and vascular diseases. Increased glomerular mesangial cell (MC) turnover, including proliferation and apoptosis, is a hallmark of CKD. Activation of p38-mitogen-activated protein kinase (p38-MAPK) has been linked to apoptosis in many cell lines. Accordingly, we studied the effect of homocysteine (Hcy) on MC p38-MAPK signalling and apoptosis. Hcy (50 microM/24 h) increased MC apoptosis as determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labelling (TUNEL) and single-stranded DNA (ssDNA) analysis. In addition to increases in pro-caspase-3 protein and caspase-3 activity, cells exposed to Hcy manifested enhanced reactive oxygen species content. Hcy increased p38-MAPK activity (fivefold), with maximal effect at 50 microM and 20 min; p38-MAPK activation was attenuated by N-acetylcysteine (Nac) and catalase (Cat), further indicating that the effect was via oxidative stress. Confocal microscopy revealed activation and nuclear translocation of p38-MAPK that was attenuated by Cat. In addition, Hcy-induced apoptosis as determined by TUNEL and ssDNA assay was abrogated by Nac, Cat, and SB203580 (p38-MAPK inhibitor). We conclude that in MC, Hcy (i) activates p38-MAPK and increases p38MAPK nuclear translocation via an oxidative stress dependent mechanism and (ii) induces DNA damage and apoptosis that is dependent on oxidative stress and p38-MAPK activation.
Assuntos
Apoptose/fisiologia , Homocisteína/fisiologia , Células Mesangiais/fisiologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Animais , Caspase 3/metabolismo , Células Cultivadas , Estresse Oxidativo/fisiologia , Ratos , Espécies Reativas de Oxigênio/metabolismoRESUMO
In this study, we examined expression of heat shock proteins (HSP) 70 and 90 in human leucocytes after moderate-to-heavy exercise. We also compared baseline levels of HSP70 and HSP90 in trained (TR) and untrained (UT) subjects. Eleven TR subjects ran on a treadmill for 1 h at 70% of maximal oxygen consumption. The HSP levels were measured prior to exercise and 15 and 24 h after exercise. Baseline HSP levels were also measured in eight UT controls. Fifteen hours and 24 h after exercise, TR subjects showed no significant increases in HSP70 (P > 0.05). The HSP90 levels also did not change (P > 0.05). Baseline HSP70 levels in TR subjects were lower than in UT subjects (2.04 +/- 0.51 ng vs. 4.52 +/- 0.95 ng, P < 0.05), while HSP90 levels were similar in TR and UT subjects. We conclude that exercise at an intensity that is within normal limits for a moderately trained individual is not a sufficient stimulus of HSP70 production in leucocytes. We also conclude that blunted levels of baseline HSP70 expression in TR subjects might be a chronic adaptation to training.
Assuntos
Exercício Físico/fisiologia , Proteínas de Choque Térmico HSP70/metabolismo , Proteínas de Choque Térmico HSP90/metabolismo , Leucócitos/metabolismo , Adaptação Fisiológica , Adulto , Western Blotting , Composição Corporal , Peso Corporal , Regulação para Baixo , Eletroforese em Gel de Poliacrilamida , Feminino , Humanos , Masculino , Consumo de OxigênioRESUMO
Although homocysteine (Hcy) inhibits angiogenesis in vivo and in vitro, the mechanism(s) underlying this phenomenon are largely unclear. The hypothesis of the present work is that Hcy, while inducing the expression of antiangiogenic factors, inhibits the production of angiogenic factors. Mouse brain microvascular endothelial cells (MVEC) were cultured in the presence and absence of 20 microM Hcy for 24 hr in serum-free medium. Cell homogenates were incubated with Trans-Signal Angiogenesis Antibody Array containing antibodies to angiogenic activators (ANG, HGF, leptin, VEGF, IL-6, IL-8, PIGF, FGF-alpha/beta, TNF-alpha and TGF-alpha) and inhibitors (IFN-gamma, IL-12, IP-10, TIMP-1 and -2). The array membranes were scanned and normalized with positive controls. Angiogenesis and formation of capillaries were measured by culturing the MVEC in Matrigels. The capillary-like structures were identified by transmission microscopy. Hcy decreased the expression of leptin, IL-6, -8, PIGF, FGF-alpha and VEGF, while the levels of anti-angiogenic IL-12, IP-10 (chemokine) and TIMP-1 were increased by Hcy. The vascular tube-like structures by MVEC were decreased by increased Hcy. However, the addition of VEGF to Hcy-treated MVEC ameliorated the decreased Hcy-mediated capillary formation. The results suggest that Hcy inhibits angiogenesis, in part, by decreasing VEGF and increasing TIMP-1.
Assuntos
Homocisteína/química , Homocisteína/metabolismo , Neovascularização Patológica , Proteômica/métodos , Inibidor Tecidual de Metaloproteinase-1/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismo , Animais , Encéfalo/irrigação sanguínea , Encéfalo/metabolismo , Capilares , Proliferação de Células , Células Cultivadas , Córtex Cerebral/metabolismo , Quimiocinas , Colágeno/farmacologia , Meios de Cultura Livres de Soro , Combinação de Medicamentos , Endotélio Vascular/metabolismo , Laminina/farmacologia , Leptina/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Microcirculação , Microscopia Eletrônica de Transmissão , Análise de Sequência com Séries de Oligonucleotídeos , Proteoglicanas/farmacologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Fatores de TempoRESUMO
Donor leukocytes play a dual role in rejection and acceptance of transplanted organs. They provide the major stimulus for rejection, and their removal from the transplanted organ prolongs its survival. Paradoxically, administration of donor leukocytes also prolongs allograft survival provided that they are administered 1 wk or more before transplantation. Here we show that administration of donor leukocytes immediately after transplantation induced long-term acceptance of completely MHC-mismatched rat kidney or liver transplants. The majority of long-term recipients of kidney transplants were tolerant of donor-strain skin grafts. Acceptance was associated with early activation of recipient T cells in the spleen, demonstrated by a rapid increase in IL-2 and IFN-gamma at that site followed by an early diffuse infiltrate of activated T cells and apoptosis within the tolerant grafts. In contrast, IL-2 and IFN-gamma mRNA were not increased in the spleens of rejecting animals, and the diffuse infiltrate of activated T cells appeared later but resulted in rapid graft destruction. These results define a mechanism of allograft acceptance induced by donor leukocytes that is associated with activation-induced cell death of recipient T cells. They demonstrate for the first time that posttransplant administration of donor leukocytes leads to organ allograft tolerance across a complete MHC class I plus class II barrier, a finding with direct clinical application.