High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy for the Metabolic Assessment of Acute Rejection After Cardiac Transplantation in Rats.

PURPOSE: To evaluate the potential of high-resolution magic angle spinning (HR-MAS) 1H nuclear magnetic resonance (NMR) spectroscopy for metabolite characterization and the differentiation of acute rejection after heart transplantation in rat models. METHODS: We transplanted syngeneic heart grafts from Lewis rats (n = 4) and allogeneic heart grafts from F344 rats (n = 4) heterotopically into Lewis recipients. On day 7 postoperatively, the transplanted hearts were harvested for ex vivo 1H NMR spectroscopy and HR-MAS 1H NMR spectroscopy. 1H NMR spectroscopy and HR-MAS 1H NMR spectroscopy were performed at 4.7 T and 11.7 T, respectively. Metabolomic profiles contributing to the differentiation of allogeneic and syngeneic graft groups were statistically assessed by orthogonal partial least squares discriminant analysis (OPLS/O2PLS-DA). Metabolite concentrations were normalized by total spectral intensities and were compared using Mann-Whitney U tests. RESULTS: One allogeneic graft that showed extensive necrotic change suggesting graft failure was excluded from the statistical analysis of the NMR spectroscopy. In the 4.7-T 1H NMR spectroscopy, the creatine peak was decreased in the allogeneic group. The PLS-DA and OPLS/O2PLS-DA score plot demonstrated good discrimination of the allogeneic graft group from syngeneic graft group. The concentrations of creatine, myo-inositol, glucose, niacinamide, hypoxanthine, inosine, and glutamine were significantly decreased in the allogeneic graft group, whereas the concentrations of glycine, phosphoethanolamine, xanthine, sn-glycero-3-phosphocholine, leucine, valine, and tyrosine were significantly increased (P < .05). CONCLUSIONS: HR-MAS 1H NMR spectroscopy can metabolically characterize the acute rejection of heart transplantation.

Histopaque provides optimal mouse islet purification kinetics: comparison study with Ficoll, iodixanol and dextran.

Islet transplantation has become a very promising treatment for type 1 diabetes. To facilitate further clinical improvements in this exciting field, rodent islets are used to evaluate new strategies and modifications. One method to purify islets is on a density gradient, although the optimal gradient component can be debated. N=6 separate mouse islet isolations were used and the resulting islets were separated and purified on either a Ficoll, Histopaque, Dextran or Iodixanol gradient. Islets were assessed for recovery, viability, purity and in vitro functionality. Aliquots were transplanted into diabetic mice to assess in vivo functionality and survival. There was no difference in the number of islets recovered across groups nor in the size of recovered islets. Use of a Ficoll or Histopaque gradient led to the most pure and viable islets in comparison to Dextran and Iodixanol. Functionally, islets isolated on a Ficoll gradient had the highest glucose-stimulated insulin release in vitro while performing equally to Histopaque and Dextran gradients in vivo. Using a Ficoll gradient, however, comes at a higher monetary cost. We recommend using a Histopaque gradient, which led to the isolation of viable and functional islets with a reduced cost as compared to a Ficoll gradient.

MRI assessment of ischemic liver after intraportal islet transplantation.

BACKGROUND: There is a recent focus on embolization of the portal vein by transplanted islets as a major cause of early graft loss. The resultant ischemia causes necrosis or apoptosis of cells within the liver. Thus, noninvasive assessment of the liver receiving the islet transplant is important to evaluate the status islet grafts. METHODS: This study used noninvasive magnetic resonance imaging (MRI) for assessment of the posttransplant ischemic liver. Syngeneic islets in streprozotocin-induced diabetic mice were used. MRI and morphological liver assessments were performed at 0, 2, and 28 days after transplantation. Histologic assessment of insulin, hypoxia induced factor 1-alpha, and apoptosis were undertaken at similar time points. RESULTS: Ischemic/necrotic regions in the liver were detected by MRI at 2 days but not at 28 days after transplantation and were confirmed histologically. Liver injury was quantified from high intensity areas on T2-weighted images. Insulin release peaked 2 days after transplantation. CONCLUSION: Onset and reversal of liver ischemia due to intraportal islet transplantation are detectable using T2-weighted MRI. These changes coincide with periods of maximum insulin release likely due to partial islet destruction. We propose that MRI, as a noninvasive monitor of graft-related ischemia, may be useful in assessment of liver and islet engraftment after intraportal islet transplantation in a clinical setting.

Assessment of nerve regeneration across nerve allografts treated with tacrolimus.

Although regeneration of nerve allotransplant is a major concern in the clinic, there have been few papers quantitatively assessing functional recovery of animals' nerve allografts in the long term. In this study, functional recovery, histopathological study, and immunohistochemistry changes of rat nerve allograft with FK506 were investigated up to 12 weeks without slaughtering. C57 and SD rats were used for transplantation. The donor's nerve was sliced and transplanted into the recipient. The sciatic nerve was epineurally sutured with 10-0 nylon. In total, 30 models of transplantation were performed and divided into 3 groups that were either treated with FK506 or not. Functional recovery of the grafted nerve was serially assessed by the pin click test, walking track analysis and electrophysiological evaluations. A histopathological study and immunohistochemistry study were done in the all of the models. Nerve allografts treated with FK506 have no immune rejection through 12 weeks. Sensibility had similarly improved in both isografts and allografts. There has been no difference in each graft. Walk track analysis demonstrates significant recovery of motor function of the nerve graft. No histological results of difference were found up to 12 weeks in each graft. In the rodent nerve graft model, FK506 prevented nerve allograft rejection across a major histocompatibility barrier. Sensory recovery seems to be superior to motor function. Nerve isograft and allograft treated with FK506 have no significant difference in function recovery, histopathological result, and immunohistochemistry changes.

Immunocompetent syngeneic cotton rat tumor models for the assessment of replication-competent oncolytic adenovirus.

Oncolytic adenoviruses as a treatment for cancer have demonstrated limited clinical activity. Contributing to this may be the relevance of preclinical animal models used to study these agents. Syngeneic mouse tumor models are generally non-permissive for adenoviral replication, whereas human tumor xenograft models exhibit attenuated immune responses to the vector. The cotton rat (Sigmodon hispidus) is susceptible to human adenovirus infection, permissive for viral replication and exhibits similar inflammatory pathology to humans with adenovirus replicating in the lungs, respiratory passages and cornea. We evaluated three transplantable tumorigenic cotton rat cell lines, CCRT, LCRT and VCRT as models for the study of oncolytic adenoviruses. All three cells lines were readily infected with adenovirus type-5-based vectors and exhibited high levels of transgene expression. The cell lines supported viral replication demonstrated by the induction of cytopathogenic effect (CPE) in tissue culture, increase in virus particle numbers and assembly of virions seen on transmission electron microscopy. In vivo, LCRT and VCRT tumors demonstrated delayed growth after injection with replicating adenovirus. No in vivo antitumor activity was seen in CCRT tumors despite in vitro oncolysis. Adenovirus was also rapidly cleared from the CCRT tumors compared to LCRT and VCRT tumors. The effect observed with the different cotton rat tumor cell lines mimics the variable results of human clinical trials highlighting the potential relevance of this model for assessing the activity and toxicity of oncolytic adenoviruses.

Assessment of 18F-FDG-leukocyte imaging to monitor rejection after pancreatic islet transplantation.

AIM: We sought to investigate the feasibility of 18F-FDG-leukocyte imaging to detect islet rejection. METHODS: Two thousand Sprague-Dawley (SD, syngeneic group) or Lewis (allogeneic group) islet equivalents were intraportally injected into SD rat recipients. Four and 7 days after transplantation, 10(8) 18F-FDG-labeled splenocytes were injected into the jugular vein. Splenocytes were harvested from naïve or sensitized (12 days after intraportal transplantation of 2000 Lewis IEQ) SD rats. Positron emission tomography (PET) imaging was started 5 minutes after splenocyte infusion and performed hourly for 4 hours. RESULTS: One hour after splenocyte injection, FDG was mainly detected in the heart and lungs. It was then further distributed to other organs, and from the second hour, the highest tracer concentration was located in the abdomen. Liver FDG uptake was similar between syngeneic, allogeneic, and sensitized allogeneic groups at 4 and 7 days after islet transplantation. DISCUSSION: No islet rejection was detected by 18F-FDG-leukocyte imaging. The amount of transplanted tissue was only few millilitres and the additional related inflammation in case of rejection is small and difficult to detect. The liver showed a relatively high spontaneous tracer uptake; the related background prevented detection of a potential increase in tracer uptake in cases of islet rejection.

Assessment of the immune response to dose of nerve allografts.

Nerve allotransplantation provides a limitless source of nerve graft material for the reconstruction of large neural defects. It does require systemic immunosuppression or induction of immune unresponsiveness to prevent allograft rejection. It is unknown whether a greater volume of nerve graft material will increase the risk of rejection or the need for more intensive immunosuppression. This study assessed the relationship between the quantity of nerve tissue transplanted and the magnitude of the resulting immune response. Forty female (BALB/c) mice were randomly assigned to two groups that received either nerve isografts (BALB/c) or nerve allografts (C57BL/6). Each group was then subdivided into two groups that received either one or 10 sciatic nerve graft inlays. Histological and immunological assessments were performed at 10 days after engraftment. Histologic analysis demonstrated greater cellular infiltration in the allograft than the isograft groups but no appreciable difference in infiltration related to quantity of transplanted nerve tissue. In vitro assessments of the immune response using mixed lymphocyte assays and limiting dilution analysis similarly demonstrated a robust immune response to allografts but no effect on quantity of transplanted nerve tissue. These data suggest that larger peripheral nerve allografts may not be subject to increased risk for rejection.

Risk assessment in adult acute lymphoblastic leukaemia before early haemopoietic stem cell transplantation with a geno-identical donor: an easy clinical prognostic score to identify patients who benefit most from allogeneic haemopoietic stem cell transplantation.

In 1402 patients allografted in Europe during the period 1990-2000 with an HLA-identical sibling in first remission (CR1), the median interval from CR1 to allotransplant (96 days) was a major prognostic factor, patients transplanted earlier having a worse outcome. We studied in depth the 414 fully evaluable patients transplanted less than 96 days after achieving CR1; in these patients, only three factors predicted for the outcome by multivariate analysis: patient age, CR1 achievement with one or more induction courses and the recipient/donor sex combination. These three factors overcame the information from cytogenetics and source of stem cells. Three prognostic groups could be identified in relation to the outcome, using a prognostic score affecting 1 to each poor risk factor (total from 0 to 3): Group 1 (good prognosis) includes patients <35 years old, achieving CR1 with one induction course and to be transplanted with any other sex combination than female to male (score 0); group 2 (intermediate) with one adverse factor (score 1); and group 3 (bad prognosis) with two or three adverse criteria (scores 2 and 3). In these three groups, the 3-year leukaemia-free survival was 56+/-5%, 48+/-4% and 29+/-4% and the overall survival was 65+/-5, 53+/-4 and 29+/-5%, respectively. Therefore, adult patients with ALL and a score of 0 or 1 are good candidates for an early transplant if they have an identical sibling donor. Patient age, response to induction and the sex of the HLA-identical family donor (if existing) are the strongest easy predictors of the outcome for an early transplant in an adult patient with ALL. No additional information is mandatory.

Late G-CSF after allogeneic bone marrow or peripheral blood stem cell transplantation: a prospective controlled trial.

Granulocyte colony-stimulating factor (G-CSF) is widely used to accelerate neutrophil recovery after allogeneic BMT or PBSC transplantation. The optimal time to start G-CSF treatment is not known. Forty-two patients undergoing allogeneic BMT or PBSC transplantation for hematological malignancies received G-CSF either on day 6 or on day 9 post transplant. The time to hematological recovery was monitored and the two groups were compared with respect to peritransplant morbidity and mortality. Recovery of the neutrophil counts to >0.1 x 10(9)/l, > 0.5 x 10(9)/l and >1.0 x 10(9)/l were not significantly different in either group. There was no difference in recovery of red blood cell and platelet counts and no difference between the two groups with respect to the number of febrile days or number of days on antibiotic treatment. Documented bacterial, viral or fungal infections did not occur more often when G-CSF treatment was started on day 9. Delaying treatment with G-CSF resulted in a significant reduction in the length of treatment from 13 to 10 days (23.1% reduction). Reducing the length of the treatment by 3 days lowered the costs by 395.40 Euro per patient. Delaying G-CSF treatment and starting on day 9 after BMT or PBSC transplantation is safe and results in a clear economic benefit.

Cost analysis of HLA-identical sibling and voluntary unrelated allogeneic bone marrow and peripheral blood stem cell transplantation in adults with acute myelocytic leukaemia or acute lymphoblastic leukaemia.

Allogeneic stem cell transplantation (SCT) is one of the most expensive medical procedures. However, only a few studies to date have addressed the costs of HLA-identical sibling transplantation and only one study has reported costs of unrelated transplantation. No recent cost analysis with a proper follow-up period and donor identification expenses is available on related or voluntary matched unrelated donor (MUD) SCT for adult AML or ALL. Therefore, we calculated direct medical (hospital) costs based on 97 adults who underwent HLA-identical sibling bone marrow transplantation (BMT) or peripheral blood stem cell transplantation (PBSCT), and patients who received a graft from a MUD between 1994 and 1999. The average costs per transplanted patient were Euro 98,334 (BMT), Euro 151,754 (MUD), and Euro 98,977 (PBSCT), including donor identification expenses, 2 years follow-up and costs of patients who were not transplanted after they had been planned to receive an allograft. The majority of these costs was generated during the hospitalisation for graft infusion. For MUD transplants, nearly one-third of these costs was spent on the search for a suitable donor. For patients who were alive after 2 years, cumulative expenses were calculated to be Euro 103,509 (BMT), Euro 173,587 (MUD), and Euro 105,906 (PBSCT).

Quantitative assessment of angiogenesis and osteogenesis after transplantation of bone: comparison of isograft and allograft bone in mice.

We performed a vital microscopic study in mice bearing dorsal skinfold chambers to characterize microvascular perfusion and leukocyte/endothelium interaction and their effects on elongation and mineralization of neonatal isograft and allograft bone. Isograft (C57/BL to C57/BL) and allograft bone (C57/ BL to BALB/C) revascularized simultaneously. However, vascular perfusion and density were lower in allograft bone than in isograft bone. Leukocyte/endothelium interaction was the same in isograft and allograft bones. Revascularization was not detected in allograft bone transplanted to presensitized recipients. Moreover, in preexisting vessels at the transplantation site, leukocyte/endothelium interaction was altered in allograft bone of presensitized recipients, despite a normal systemic leukocyte count. Femoral growth resulting from thickening of both epiphyses did not differ between experimental groups, however, mineralization occurred in isograft bone only. Isograft bone was histologically intact, allograft bone hypovital and allograft bone in presensitized recipients necrotic 12 days after implantation. Our findings suggest that graft incorporation or rejection is mediated by the microvasculature and that presensitizing of recipients accelerates rejection of allograft bone.

In vivo microscopic assessment of cremasteric microcirculation during hindlimb allograft rejection in rats.

Experimental and clinical studies of vascular allogenic extremity transplantation have yielded disappointing results and have not been clinically useful. With recent advances in transplantation immunology, considerable interest has focused on the understanding of leukocyte-endothelial interaction at the microcirculatory level. The objective of this study was to characterize the alterations in leukocyte-endothelial interaction in the early stages of rat hindlimb allograft rejection. To study the changes at the microcirculatory level, a new microsurgical model was developed; the cremaster muscle was incorporated into the transplanted hindlimb. The purpose of this study was to report on the microcirculatory changes during rat hindlimb allograft rejection. A total of 24 transplantations were performed among the four experimental groups. In a control group, 12 rat hindlimb-cremaster grafts were transplanted between genetically identical animals, Lewis to Lewis. Microcirculatory measurements of graft survival were taken at 24 hours (group 1A, n = 6) and at 72 hours (group 1B, n = 6). In the rejection control group, 12 transplantations were performed across a major histocompatibility barrier between Lewis-Brown Norway and Lewis rats. Microcirculatory measurements were taken at 24 (group 2A, n = 6) and 72 hours (group 2A, n = 6) as above. The following parameters were evaluated to discover the leukocyte-endothelial interaction: endothelial edema index and the number of rolling, adherent, and transmigrating leukocytes and lymphocytes in the postcapillary venule. Physical signs of limb rejection, such as edema, erythema, scaling, plaque formation on the skin, hair loss, and skin surface temperature, were monitored. Microcirculatory signs of rejection included the following. There was a significant increase in the number of adherent leukocytes in allograft transplants at both 24 hours (205 percent; 2.05 +/- 0.38) and 72 hours (431 percent; 9.11 +/- 3.41) when compared with isograft controls (1.00 +/- 0.89 at 24 hours; 2.11 +/- 0.34 at 72 hours) (p < 0.05). The activation of leukocyte transmigration increased more than 7-fold in muscle allografts at 24 hours (0.55 +/- 0.25 versus 4.16 +/- 1.89) and more than 6-fold at 72 hours (0.72 +/- 0.38 versus 4.38 +/- 1.28) after transplantation (p < 0.05). Endothelial edema index, a measure of endothelial swelling and cellular deposit accumulation, increased more than 119 percent in the allograft group 72 hours after transplantation (1.23 +/- 0.07 versus 1.46 +/- 0.09) (p < 0.05). The first clinical signs of limb rejection were scaling of the skin or hair loss; they were observed between the seventh and ninth postoperative days. The composite rat hindlimb-cremaster model presented in this study introduces a new in vivo approach to monitor acute graft rejection using the intravital microscopy system. This is a valuable model for defining the timing, sequence, and correlation between immunologic events and clinical signs during the acute phase of allograft rejection.

In vivo assessment of the influence of cold preservation time on microvascular reperfusion injury after experimental small bowel transplantation.

BACKGROUND: This study describes the impact of prolonged cold storage on microvascular reperfusion injury of transplanted rat small bowel isografts. METHODS: In vivo fluorescence microscopy was used to assess intestinal microcirculation after 6, 12, 18 and 24 h of cold (4 degrees C) ischaemia in University of Wisconsin solution and 20-90 min of reperfusion. Sham-operated animals served as controls. RESULTS: Whereas 6 and 12 h of ischaemia did not affect functional capillary density of the intestinal graft mucosa, villous perfusion was significantly impaired after 18 and 24 h of cold preservation. Similarly, microvascular perfusion of circular and longitudinal muscle was not affected after 6 h, but deteriorated following prolonged cold ischaemia. Leucocyte-endothelial cell interaction in submucosal venules was significantly enhanced after 6 h of ischaemia with peak values after 12 and 18 h. A progressive reduction of lymphatic capillary drainage indicated an ischaemia time-related deterioration in graft function. CONCLUSION: The results provide evidence that leucocyte-endothelial cell interaction in submucosal venules of the transplanted intestine is a primary step in the manifestation of reperfusion injury following short periods of cold ischaemia.

In vivo microscopic assessment of hepatic microcirculation during liver allograft rejection in the rat.

The hemodynamic alterations in hepatic microvasculature during acute rejection of rat liver allografts was studied using in vivo fluorescence microscopy. ACI rat livers were transplanted into Lewis (allograft) or ACI (isograft) recipients. Microscopy was performed on days 3 (n = 7) and 6 (n = 7) in allografts, and on day 6 (n = 7) in isografts. Naive ACI livers (n = 7) served as nontransplant controls. Changes in sinusoidal blood perfusion, microvascular structure, and leukocyte-endothelial interactions were observed and quantitated. Six days after transplantation, acinar perfusion was markedly impaired in allografts and was accompanied by a lower percentage of perfused sinusoids (59 +/- 8%, mean +/- SEM, P < 0.01) relative to isografts (89 +/- 3%) and nontransplant controls (100 +/- 0%). The hepatic cord width in allografts was significantly greater than in isografts or in nontransplant controls, indicating swelling of parenchymal and sinusoidal lining cells. Furthermore, the number of leukocytes adhering to the sinusoidal endothelium significantly increased in allografts. Adherence to postsinusoidal venules was more prominent in allograft livers (4025 +/- 1400/mm2 of vascular endothelial surface) compared with that in isografts (574 +/- 77/mm2) and nontransplant controls (185 +/- 28/mm2). These microcirculatory alterations in allografts were significant even on day 3. The results show extensive abnormalities of the microcirculatory hemodynamics in rejecting liver allografts which were associated with increased leukocyte adherence to microvascular endothelium. Our findings may provide strategic information for the prevention and treatment of allograft rejection.

Experimental orthotopic transplantation of vascularized skeletal allografts: functional assessment and long-term survival.

Vascularized skeletal tissue allografts would greatly expand the domain of reconstructive surgery. Few studies to date have examined the functional aspects of these allografts or their long-term fate. An orthotopic transplant model of rat distal femur and surrounding muscular cuff was developed to assess graft function in fracture healing and weight bearing. Isografts (RT1l to RT1l, n = 40), weak-barrier allografts (RT1l to RT1lv, n = 40), and strong-barrier allografts (RT1l to RT1n, n = 40) were transplanted. As the histocompatibility barrier increased between the donor and recipient animals, the graft viability and performance deteriorated according to radiographic, histologic, and immunologic analyses. Administration of cyclosporine led to survival of strong-barrier allografts similar to that of isografts. A long-term study of these allografts (RT1l to RT1n) was then performed on various immunosuppressive regimens. After an initial 10-week course of cyclosporine to achieve bony union and remodeling, subsequent cessation (n = 20) or intermittent "pulsing" (n = 20) of the immunosuppressant was insufficient in maintaining graft survival. However, graft viability and function were preserved through 1 year on continuous daily cyclosporine (n = 32). There was no evidence of host renal or hepatic toxicity by serum chemistry or histologic sections. Thus long-term survival of functional skeletal allografts was achieved in this orthotopic model without significant host toxicity from immunosuppression.

Assessment of the dynamics of allograft rejection utilizing Tc-99m labeled lymphocytes.

The feasibility of utilizing technetium 99m (Tc-99m) lymphocytes labeled by a modified stannous chloride technique for the assessment of cardiac allograft rejection was examined. Syngeneic lymphocytes were labeled with Tc-99m at 125 microCi per 10(7) cells. Mean labeling efficiency was 67 +/- 17%, n = 44. Two groups of rats allogeneic (ALLO) (ACI/Lewis) and syngeneic (SYN) (Lewis/Lewis) were injected with labeled cells at two, four, five, and seven days post cardiac graft. At 20 hr post-injection, transplant and native hearts were harvested for radioanalysis and histology. Ratio of percent dose per gram transplant heart to native heart (T/N) revealed a significant difference between ALLO (T/N = 2.7 +/- 0.23, n = 5) and SYN (T/N = 1.73 +/- 0.12, n = 5) at two days P[F] = 0.0045. Maximum difference occurred at five days with ALLO mean T/N of 6.40 +/- 0.54, n = 5 (P[F] = 0.0001). There was no significant difference at seven days post graft with ALLO 2.85 +/- 0.30, n = 5 and SYN 2.02 +/- 0.05, n = 5 (P[F] = 0.0166). SYN rat T/Ns did not change significantly (mean 1.83 +/- 0.10, n = 18) at the various time periods.

Immune response against P815X2 mastocytoma growing in syngeneic DBA/2 mice. III. Morphometric assessment of the dynamic changes in post-capillary venules as regulatory elements of lymphocyte recirculation in tumor-draining lymph nodes.

To evaluate the dynamics of lymphocyte recirculation in tumor-bearing mice, the post-capillary venules (PCV) were subjected to quantitative measurements in the regional (RLN) and nonregional (NRLN) lymph nodes during the progression of P815X2 mastocytoma in syngeneic DBA/2 mice. Mice were sacrificed at two-day intervals, and RLNs and NRLNs were analysed for their content of B- and T-lymphocytes and their subsets, demonstrated by immunoperoxidase technique using monoclonal antibodies; Anti-Thy 1.2 (T cells), Anti-Lyt 1 (T-helper cells), Anti-Lyt 2 (T-suppressor cells), and Anti-I-Ad (B cell) antigens, separately in the B- and T-cell compartments. In the PCVs, migration index (MI) and endothelial height (Hend) were measured. There was a biphasic elevation of MI in the RLNs, as compared with only a late rise in the NRLNs, reaching the peak (1.54) on day 14. In RLNs, there was a sharp reduction in Hend starting from the values (6.37 microns) on day 2, down to 4.79 microns on day 8. This is followed by rapid elevation close to the second-day values, e.g. 6.07 on day 10. The changes in MI paralleled the early influx of B cells, as evidenced by the decrease of Thy 1.2+/I-Ad+ cell ratio and a late recruitment of T cells as indicated by the elevation of that ratio as well as the Hend values in both the RLNs and NRLNs. The present experiment shows that morphology of PCVs in the RLNs and in NRLNs of P815X2-bearing mice is subjected to alterations reflecting the dynamics of lymphocyte recruitment into these organs. When combined with lymphocyte subset enumeration using monoclonal antibodies, the quantitative analysis of the PCVs permits predictions to be made on the recirculatory activity of these cell populations during the tumor progression.