Prolongation of xenograft survival using monoclonal antibody CD45RB and cyclophosphamide in rat-to-mouse kidney and heart transplant models

BACKGROUND

Intrigued by the finding that a monoclonal antibody (mAb) directed against the B exon of restricted CD45 (CD45RB mAb) induced renal allograft tolerance in the mouse model, we hypothesized that CD45RB mAb may prevent xenograft rejection. We explored the role of CD45RB mAb in preventing xenograft rejection in rat-to-mouse kidney and heart transplant models.

METHODS

Mice with rat kidney and heart xenografts were treated with a short course of mAb, cyclosporine, cyclophosphamide, or mAb + cyclophosphamide combination therapy. Untreated heart and kidney xenografts served as controls.

RESULTS

Untreated controls developed acute vascular and cellular rejection rapidly with a median survival time of only 6 days. Long-term kidney (median survival time = 70 days) and heart xenograft survival (median survival time = 65 days) was achieved using the combination therapy of mAb + cyclophosphamide. One-third of the kidney recipients with combination therapy survived 100 days. Immunohistochemistry and xenospecific-antibody analysis demonstrated that combination therapy remarkably reduced IgG and IgM deposition and also inhibited CD4+, CD8+, and Mac-1+ cell infiltration at early stages. This therapy, however, did not induce tolerance in this model as evoked xenoreactive antibodies and cellular responses may be the cause of late xenograft failure.

CONCLUSION

A short course of CD45RB mAb combined with cyclophosphamide effectively inhibits cellular and humoral immunoresponses and remarkably prolongs xenograft survival in rat-to-mouse heart and kidney transplant models.

Prevention of experimental allergic encephalomyelitis by an antibody to CD45RB

CD45 is involved in the regulation of lymphocyte activation, and it has been demonstrated that ligation of CD45 induces apoptosis of T and B lymphocytes. Recently anti-CD45RB antibody therapy was shown to block acute allograft rejection in a mouse model of transplantation. Therefore, we wanted to examine the effects of anti-CD45RB antibody treatment on the course of an autoimmune disorder, experimental allergic encephalomyelitis (EAE), a Th1-mediated process. Mice immunized with myelin basic protein and treated with anti-CD45RB antibody did not develop EAE. Histologically, there was no evidence of lymphocytic infiltrates in the central nervous system. T cell proliferation and TNF-alpha production were significantly decreased in anti-CD45RB-treated mice. Furthermore, there was a significant reduction in the production of other Th1 cytokines including interferon-gamma and IL-2, but not IL-4 or IL-6. However, levels of a number of adhesion markers or markers of activation such as VLA-4 and LFA-1 on T cells were no different in treated versus control animals. Thus, anti-CD45RB can prevent EAE and appears to do so by altering T cell proliferation and cytokine production.

Homing potentials of circulating lymphocytes in humans depend on the site of activation: oral, but not parenteral, typhoid vaccination induces circulating antibody-secreting cells that all bear homing receptors directing them to the gut

Specific Ab-secreting cells (ASC) appear in the human blood as a response to oral and parenteral vaccination. The actual contribution of these cells to the defense of the body depends on their final effector site. The homing potentials of mucosally and parenterally induced ASC were compared by examining the homing receptor (HR) expression of circulating specific ASC in the blood of volunteers vaccinated orally or parenterally with the same Ag, Salmonella typhi Ty21a. Circulating lymphocytes were separated into receptor-positive and -negative populations, and the numbers of specific ASC were assayed. The alpha4 beta7 integrin, which acts as a gut HR, was expressed on all (99%) of the mucosally activated ASC, but on only 58% of the parenterally induced ASC or 58% of all Ig-secreting cells of the unvaccinated controls. L-selectin, the peripheral lymph node HR, showed an inverse distribution; it was found on 42% of mucosally activated ASC and on 86% of parenterally induced ASC. These results reveal that all of the circulating ASC after oral vaccination are committed to migrate to the mucosal compartment of the immune system, strongly arguing for a recirculation of activated mucosal cells in humans. By contrast, ASC induced by parenteral vaccination with the same Ag are mostly directed to the systemic compartment, yet a part of them has mucosal homing attitudes as well. These differences indicate that the site of Ag encounter determines the homing potential of the cell.

Homing potentials of circulating lymphocytes in humans depend on the site of activation: oral, but not parenteral, typhoid vaccination induces circulating antibody-secreting cells that all bear homing receptors directing them to the gut

Specific Ab-secreting cells (ASC) appear in the human blood as a response to oral and parenteral vaccination. The actual contribution of these cells to the defense of the body depends on their final effector site. The homing potentials of mucosally and parenterally induced ASC were compared by examining the homing receptor (HR) expression of circulating specific ASC in the blood of volunteers vaccinated orally or parenterally with the same Ag, Salmonella typhi Ty21a. Circulating lymphocytes were separated into receptor-positive and -negative populations, and the numbers of specific ASC were assayed. The alpha4 beta7 integrin, which acts as a gut HR, was expressed on all (99%) of the mucosally activated ASC, but on only 58% of the parenterally induced ASC or 58% of all Ig-secreting cells of the unvaccinated controls. L-selectin, the peripheral lymph node HR, showed an inverse distribution; it was found on 42% of mucosally activated ASC and on 86% of parenterally induced ASC. These results reveal that all of the circulating ASC after oral vaccination are committed to migrate to the mucosal compartment of the immune system, strongly arguing for a recirculation of activated mucosal cells in humans. By contrast, ASC induced by parenteral vaccination with the same Ag are mostly directed to the systemic compartment, yet a part of them has mucosal homing attitudes as well. These differences indicate that the site of Ag encounter determines the homing potential of the cell.

Pattern of liver, kidney, heart, and intestine allograft rejection in different mouse strain combinations

With advances in microsurgery and molecular biology, the mouse model for organ transplantation has become increasingly popular. However, knowledge about these models is limited, as only a small number of centers have experience with murine models. In this study, we compared the rejection pattern after liver, kidney, heart, and small bowel transplantation in the three different mouse strain combinations: (1) C57BL/6 (H2b)-->BALB/c (H2d), (2) BALB/c (H2d)-->CBA (H2k), and (3) C57BL/6-->C3H/HeN (H2k). Our study demonstrated that mouse allograft survival varies depending on the organ graft and on the donor-recipient strain combinations. The majority of liver allografts were spontaneously accepted despite complete MHC disparity. A mixed pattern of acute rejection and acceptance occurred in kidney recipients depending on the donor-recipient strain combination. All the heart grafts developed rejection and all the intestinal grafts were rapidly rejected with no spontaneous acceptance. The criteria for rejection, the potential applications, and the limitations of each model are discussed. The models described in this article provide a number of useful choices for organ transplantation research.

Interaction of monocytoid cells with the mucosal addressin MAdCAM-1 via the integrins VLA-4 and LPAM-1

The differentiation of myeloid cells into macrophages and granulocytes is accompanied by marked changes in adhesive phenotype. Here we seek to understand the regulation of expression and functionality of the VLA-4 (alpha 4 beta 1), LPAM-1 (alpha 4 beta 7) and HML-1 (alpha E beta 7) integrins on monocytes/macrophages and granulocytes, given that these integrins including LFA-1 (alpha L beta 2) mediate the entry, retention and signalling events of pathogenic leucocytes within chronically inflamed tissues. Phorbol ester-induced monocytic differentiation of the promyelocyte cell line HL60 led to increases in the steady-state levels of beta 2 and beta 7 mRNA transcripts, requiring a period of 10 and 24 h, respectively, of de novo protein synthesis. There was a parallel de novo expression of LPAM-1 on the cell surface, despite the fact that alpha 4 mRNA transcripts were rapidly down-regulated. At 72 h, HML-1 was not coexpressed with LPAM-1 on HL60 cells, although it was weakly expressed on peripheral blood monocytes/macrophages after a prolonged period of in vitro culture. Retinoic acid-induced granulocytic differentiation of HL60 cells led to the appearance of low levels of LPAM-1 at the cell surface. LPAM-1 was not found expressed on peripheral blood neutrophils, raising the possibility that it is transiently expressed during granulocyte differentiation. In accord with the above findings, differentiated monocytes and HL60 cells bound to recombinant MAdCAM-1 in an alpha 4- and beta 7-integrin-dependent fashion, whereas a population of undifferentiated HL60 cells and Mn(+2)-activated monocytes bound in an alpha 4-integrin-dependent beta 7-integrin-independent manner via VLA-4 expressed abundantly at all stages of differentiation. Four h after attachment, some of these VLA-4+ LPAM-1- HL60 cells could be seen to start spreading. These finding suggest that MAdCAM-1 can bind to VLA-4 when LPAM-1 is absent, and thus has the potential to recruit both VLA-4-bearing monocytes and VLA-4+ LPAM-1+ macrophages into chronically inflamed tissues.

Processing of chimeric antisense oligonucleotides by human vascular smooth muscle cells and human atherosclerotic plaque. Implications for antisense therapy of restenosis after angioplasty

BACKGROUND

Antisense oligonucleotides have been used in animals to inhibit the accumulation of vascular smooth muscle cells (VSMCs) after arterial injury. This has raised prospects for an oligonucleotide-mediated approach to prevent restenosis in patients undergoing angioplasty. However, little is known about the processing of oligonucleotides by human VSMCs or their bioavailability in human atherosclerotic tissue.

METHODS AND RESULTS

Oligonucleotides were synthesized with a mixture of unmodified and sulfur-modified linkages (S-chimeric oligonucleotides). These were more stable than unmodified oligonucleotides and could be recovered from within human VSMCs after 36 hours. Oligonucleotide antisense to human proliferating cell nuclear antigen mRNA specifically reduced DNA synthesis (P < .01) and proliferating cell nuclear antigen protein content (P < .05) in human VSMCs. Confocal microscopy of both live and fixed cells showed modest oligonucleotide uptake that was primarily nuclear. Surprisingly, cationic liposomes did not enhance nuclear uptake but led to extensive, punctated cytoplasmic loading without an enhanced antisense effect. Oligonucleotides incubated with human coronary atherosclerosis fragments associated with cells within 1 hour, despite the presence of abundant extracellular matrix.

CONCLUSIONS

S-chimeric oligonucleotides are stable and can specifically inhibit gene expression in human VSMCs. Nuclear transport is a feature of oligonucleotide processing by human VSMCs, indicating a potential influence at the nuclear level rather than with cytoplasmic mRNA. Cationic liposomes increased oligonucleotide uptake but not intracellular bioavailability, and S-chimeric oligonucleotides can be incorporated into cells within human atherosclerotic plaque, despite the presence of a dense extracellular matrix.

Crohn's disease, ulcerative colitis, and normal intestinal lymphocytes express integrins in dissimilar patterns

BACKGROUND/AIMS

The integrin family of adhesion molecules on intestinal lamina propria mononuclear cells (LPMNC) was studied using fluorescence-activated cell cytometry. These molecules are implicated in extravascular cell migration and are important regulators of disease.

METHODS

Using fluorescence-activated cell cytometry, B- and T-cell subsets in the intestines of 10 normal patients, 11 patients with Crohn's disease, and 8 patients with ulcerative colitis were stained with monoclonal antibodies to a panel of integrins.

RESULTS

Expression of alpha integrins on CD3+ T cells and CD19+ B cells was different in normal and inflammatory bowel disease LPMNC. Ulcerative colitis T cells expressed less beta 1 and alpha 4 and significantly more alpha 2 and alpha 6. There was a difference in alpha 4 and beta 1 expression between LPMNC B cells from Crohn's disease and normal intestines. Sixteen percent of CD19+ LPMNC B cells from Crohn's and 19% of ulcerative colitis LPMNC expressed alpha 2. Crohn's and ulcerative colitis CD19+ LPMNC B cells expressed more alpha 5 integrin than normal specimens. CD3+ T cells and CD19+ B cells expressed alpha 6 only in ulcerative colitis. Ulcerative colitis and Crohn's disease CD19+ LPMNC expressed less alpha 4, consistent with their reciprocal increases of alpha 5 and alpha 2. A difference in beta 7 (Peyer's patch specific) antigen was observed between inflammatory bowel disease and normal LPMNC for both CD3+ and CD19+ LPMNC.

CONCLUSIONS

These findings identify the differences of lymphocyte homing capability in inflammatory bowel disease and normal intestine.

Monocyte membrane ferritin in hemochromatosis

To further evaluate a possible abnormality in the reticuloendothelial cells in hemochromatosis, the binding of a monoclonal anti-human liver ferritin antibody to monocytes was studied in 19 patients with hemochromatosis, 8 patients with secondary iron overload, 1 patient with hyperferritinemia without iron overload, and 15 normal volunteers. Binding of the antibody to the monocytes was analyzed using a fluorescence-activated cell sorter (FACS). Binding of the anti-ferritin antibody to monocytes was demonstrated in 34.7 +/- 4.5% (mean +/- standard error) of the monocytes in untreated hemochromatosis patients (mean serum ferritin = 2294 +/- 415 micrograms/L), 6.75 +/- 2.03% in treated hemochromatosis patients (mean serum ferritin = 263 +/- 85 micrograms/L), 12.3 +/- 2.7% of the monocytes in the secondary iron overload patients (mean serum ferritin = 2476 +/- 867 micrograms/L), 4.1% in the patient with hyperferritinemia (serum ferritin = 1192) and 4.1 +/- 0.5% of the monocytes in the normal volunteers (mean serum ferritin = 55.2 +/- 11.9 micrograms/L). % binding of anti-ferritin antibody was significantly greater in hemochromatosis patients compared to patients with secondary iron overload (p less than 0.05) despite a comparable degree of iron overload in the secondary iron overload group. The addition of exogenous human ferritin to samples from treated hemochromatosis patients and normal volunteers did not significantly increase the % of monocytes binding anti-ferritin antibody. These results suggest that monocytes from iron-loaded hemochromatosis patients express increased surface ferritin which may represent release of ferritin and a metabolic defect characteristic of hemochromatosis.

Expression of transferrin receptors on monocytes in hemochromatosis

To assess whether an abnormality in transferrin receptor expression or regulation could represent an underlying metabolic defect in the reticuloendothelial (RE) system in hemochromatosis, monocytes were analyzed for the expression of the transferrin receptor using a monoclonal antibody (Act II) to the transferrin receptor (CD71) and flow cytometric analysis. Hemochromatosis patients (n = 14), and normal volunteers with no clinical evidence of iron overload (n = 14) were studied. A significant inverse relationship was observed for the relationship between the expression of transferrin receptor on monocytes and log(hepatic iron concentration) in hemochromatosis patients (r = -0.59, P less than .02) and also for the relationship between the expression of transferrin receptor and log(serum ferritin) in normal volunteers (r = -0.90, P less than .001). There was no significant difference in the mean expression of monocyte transferrin receptor between hemochromatosis patients and normal volunteers. However, the expression of the transferrin receptor in hemochromatosis patients was disproportionately higher than would be predicted from the relationship between serum ferritin and transferrin receptor expression in normal volunteers. The inverse relationship of the monocyte transferrin receptor relative to body iron stores in hemochromatosis is consistent with observations in other tissues, and suggests that non-transferrin iron metabolism, including ferritin, requires further investigation in the RE cell in hemochromatosis.