Immunohistochemical study of skin lesions in acute and chronic graft versus host disease following bone marrow transplantation

Histopathologic and immunophenotypic features of cutaneous solid organ transplant-associated graft-vs-host disease: Comparison with acute hematopoietic cell transplant-associated graft-vs-host disease and cutaneous drug eruption

BACKGROUND

Although it is relatively common after hematopoietic cell transplant (HCT), graft-vs-host disease (GVHD) is a rare complication following solid organ transplantation (SOT).

METHODS

This study evaluated skin biopsy specimens from five cases of SOT GVHD, 15 cases of HCT GVHD, and 15 cases of cutaneous drug eruption. Immunohistochemical staining for CD3, CD4, CD8, T-bet, and GATA-3 was performed to examine the density and immune phenotype of skin-infiltrating lymphocytes.

RESULTS

Similar to HCT GVHD, the predominant histopathologic findings in skin biopsy specimens of SOT GVHD were widespread vacuolar interface dermatitis with scattered necrotic keratinocytes. However, the density of dermal inflammation was considerably higher in SOT GVHD. Features that were more predictive of a cutaneous drug eruption over GVHD included spongiosis, confluent parakeratosis, and many eosinophils. Involvement of the hair follicle epithelium was seen in all three disorders. Both forms of cutaneous GVHD showed a predominance of Th1 (CD3+/T-bet+) lymphocytes within the inflammatory infiltrates. This shift was more pronounced in SOT GVHD, particularly among intraepidermal T-cells.

CONCLUSIONS

SOT GVHD shares many histopathologic features with HCT GVHD. However, SOT GVHD has a greater tendency to develop brisk lichenoid inflammation.

Unraveling the Mechanisms of Cutaneous Graft-Versus-Host Disease

The skin is the most common target organ affected by graft-versus-host disease (GVHD), with severity and response to therapy representing important predictors of patient survival. Although many of the initiating events in GVHD pathogenesis have been defined, less is known about why treatment resistance occurs or why there is often a permanent failure to restore tissue homeostasis. Emerging data suggest that the unique immune microenvironment in the skin is responsible for defining location- and context-specific mechanisms of injury that are distinct from those involved in other target organs. In this review, we address recent advances in our understanding of GVHD biology in the skin and outline the new research themes that will ultimately enable design of precision therapies.

Tissue Damage Caused by Myeloablative, but Not Non-Myeloablative, Conditioning before Allogeneic Stem Cell Transplantation Results in Dermal Macrophage Recruitment without Active T-Cell Interaction

Introduction

Conditioning regimens preceding allogeneic stem cell transplantation (alloSCT) can cause tissue damage and acceleration of the development of graft-versus-host disease (GVHD). T-cell-depleted alloSCT with postponed donor lymphocyte infusion (DLI) may reduce GVHD, because tissue injury can be restored at the time of DLI. In this study, we investigated the presence of tissue injury and inflammation in skin during the period of hematologic recovery and immune reconstitution after alloSCT.

Methods

Skin biopsies were immunohistochemically stained for HLA class II, CD1a, CD11c, CD40, CD54, CD68, CD86, CD206, CD3, and CD8. HLA class II-expressing cells were characterized as activated T-cells, antigen-presenting cells (APCs), or tissue repairing macrophages. In sex-mismatched patient and donor couples, origin of cells was determined by multiplex analysis combining XY-FISH and fluorescent immunohistochemistry.

Results

No inflammatory environment due to pretransplant conditioning was detected at the time of alloSCT, irrespective of the conditioning regimen. An increase in HLA class II-positive macrophages and CD3 T-cells was observed 12–24 weeks after myeloablative alloSCT, but these macrophages did not show signs of interaction with the co-localized T-cells. In contrast, during GVHD, an increase in HLA class II-expressing cells coinciding with T-cell interaction was observed, resulting in an overt inflammatory reaction with the presence of activated APC, activated donor T-cells, and localized upregulation of HLA class II expression on epidermal cells. In the absence of GVHD, patient derived macrophages were gradually replaced by donor-derived macrophages although patient-derived macrophages were detectable even 24 weeks after alloSCT.

Conclusion

Conditioning regimens cause tissue damage in the skin, but this does not result in a local increase of activated APC. In contrast to the inflamed situation in GVHD, when interaction takes place between activated APC and donor T-cells, the tissue damage caused by myeloablative alloSCT results in dermal recruitment of HLA class II-positive tissue repairing macrophages co-existing with increased numbers of patient- and donor-derived T-cells, but without signs of specific interaction and initiation of an immune response. Thus, the local skin damage caused by the conditioning regimen appears to be insufficient as single factor to provoke GVHD induction.

Lichenoid Dermatitis of the Vulva: Diagnosis and Differential Diagnosis for the Gynecologic Pathologist

Inflammatory processes affecting the vulva may present a unique challenge due to location specific changes. Different factors are behind the intricacy in the presentation of vulvar dermatoses. First, the vulva is lined by different epithelia (hair-bearing keratinized epithelium, modified mucosa, and mucosa). Furthermore, among other factors, this organ is exposed to friction, occlusion, and trauma. Lastly, as there is a tendency to look for health care advice at an advanced stage of the disease, the lesion may be modified by secondary changes due to self-treatment. This article describes the clinical presentation and pathologic features of vulvar dermatoses with a lichenoid pattern and highlights practical points for their diagnoses.

Histological assessment of the sclerotic graft-versus-host response in the humanized RAG2-/-γc-/- mouse model

Graft-versus-host disease (GVHD) remains a frequently occurring and difficult-to-treat complication in human allogeneic stem cell transplantation. Murine transplantation models are often used to study and understand the complex pathogenesis of GVHD and to explore new treatment strategies. Although GVHD kinetics may differ in murine and human models, adequate models are essential for identification of the crucial factors responsible for the major pathology in GVHD. We present a detailed description of the specific histological features of a graft-versus-host-induced fibrotic response in xenogeneic RAG2(-/-)γc(-/-) mice after total body irradiation and injection with human peripheral blood mononuclear cells. We describe the full morphological features of this reaction, including a detailed analysis of the specific tissue infiltration patterns of the human peripheral blood mononuclear cells. Our data show the development of fibrosis, predominantly near blood vessels, and reveal different cell populations and specific cell migration patterns in the affected organs. The combination of immunohistochemical cell characterization and mRNA expression analysis of both human (donor)- and murine (host)-derived cytokines reveals an interaction between host tissues and donor-derived cells in an entangled cytokine profile, in which both donor- and host-derived cytokines contribute to the formation of fibrosis.

Villitis of unknown etiology is associated with a distinct pattern of chemokine up-regulation in the feto-maternal and placental compartments: implications for conjoint maternal allograft rejection and maternal anti-fetal graft-versus-host disease

The co-presence of histoincompatible fetal and maternal cells is a characteristic of human placental inflammation. Villitis of unknown etiology (VUE), a destructive inflammatory lesion of villous placenta, is characterized by participation of Hofbauer cells (placental macrophages) and maternal T cells. In contrast to acute chorioamnionitis of infection-related origin, the fundamental immunopathology of VUE is unknown. This study was performed to investigate the placental transcriptome of VUE and to determine whether VUE is associated with systemic maternal and/or fetal inflammatory response(s). Comparison of the transcriptome between term placentas without and with VUE revealed differential expression of 206 genes associated with pathways related to immune response. The mRNA expression of a subset of chemokines and their receptors (CXCL9, CXCL10, CXCL11, CXCL13, CCL4, CCL5, CXCR3, CCR5) was higher in VUE placentas than in normal placentas (p < 0.05). Analysis of blood cell mRNA showed a higher expression of CXCL9 and CXCL13 in the mother, and CXCL11 and CXCL13 in the fetus of VUE cases (p < 0.05). The median concentrations of CXCL9, CXCL10, and CXCL11 in maternal and fetal plasma were higher in VUE (p < 0.05). Comparison of preterm cases without and with acute chorioamnionitis revealed elevated CXCL9, CXCL10, CXCL11, and CXCL13 concentrations in fetal plasma (p < 0.05), but not in maternal plasma with chorioamnionitis. We report for the first time the placental transcriptome of VUE. A systemic derangement of CXC chemokines in maternal and fetal circulation distinguishes VUE from acute chorioamnionitis. We propose that VUE be a unique state combining maternal allograft rejection and maternal antifetal graft-vs-host disease mechanisms.

Composite Tissue Allotransplantation: Classification of Clinical Acute Skin Rejection

BACKGROUND

Composite tissue allotransplantation (CTA) is a recently introduced option for limb replacement and reconstruction of other nonreconstructible tissue defects. As with recipients of other allotransplants, CTA recipients can experience rejection episodes that are presumed to be mediated by immune mechanisms similar to those affecting solid organ grafts. However, a systematic examination of this process has not been performed, and there are no standardized criteria for the description of severity or type of rejection.

METHODS

We collected biopsies from human limb allografts and abdominal walls in various stages of rejection for histological and immunohistochemical analysis to formulate a CTA rejection scheme. Biopsies were ranked by severity and reproducibility of the system was tested using a second set of biopsies. Tissue slides were examined blindly by three pathologists and the nonparametric Kendall coefficient of concordance (W) was used to assess the amount of agreement among the pathologists in their classification grades.

RESULTS

Rejection initially appeared as a perivascular infiltrate progressing to involve the dermis. Arteritis was observed only in the medium to large size arteries of the subcutis. Myositis was seen occasionally. Perineural involvement without frank neuritis was present in advanced rejection. The infiltrate was predominantly CD4+ in milder cases and CD8+ in advanced cases. HLA-DR was minimally expressed in keratinocytes even in severe rejection. Kendall's W was 0.9375 (p< or =0.0001).

CONCLUSIONS

Based on this survey, we proposed an initial classification system for acute rejection in the skin of a CTA and demonstrated that this system is easily reproduced by independent pathologists.

Host-reactive CD8+ memory stem cells in graft-versus-host disease

Graft-versus-host disease (GVHD) is caused by alloreactive donor T cells that trigger host tissue injury. GVHD develops over weeks or months, but how this immune response is maintained over time is unknown. In mouse models of human GVHD, we identify a new subset of postmitotic CD44(lo)CD62L(hi)CD8(+) T cells that generate and sustain all allogeneic T-cell subsets in GVHD reactions, including central memory, effector memory and effector CD8(+) T cells, while self-renewing. These cells express Sca-1, CD122 and Bcl-2, and induce GVHD upon transfer into secondary recipients. The postmitotic CD44(lo)CD62L(hi)CD8(+) T cells persist throughout the course of GVHD, are generated in the initial phase in response to alloantigens and dendritic cells and require interleukin-15. Thus, their long life, ability to self-renew and multipotentiality define these cells as candidate memory stem cells. Memory stem cells will be important targets for understanding and influencing diverse chronic immune reactions, including GVHD.

Alloreactive memory T cells are responsible for the persistence of graft-versus-host disease

Graft-vs-host disease (GVHD) is caused by a donor T cell anti-host reaction that evolves over several weeks to months, suggesting a requirement for persistent alloreactive T cells. Using the C3H.SW anti-C57BL/6 (B6) mouse model of human GVHD directed against minor histocompatibility Ags, we found that donor CD8(+) T cells secreting high levels of IFN-gamma in GVHD B6 mice receiving C3H.SW naive CD8(+) T cells peaked by day 14, declined by day 28 after transplantation, and persisted thereafter, corresponding to the kinetics of a memory T cell response. Donor CD8(+) T cells recovered on day 42 after allogeneic bone marrow transplantation expressed the phenotype of CD44(high)CD122(high)CD25(low), were able to homeostatically survive in response to IL-2, IL-7, and IL-15 and rapidly proliferated upon restimulation with host dendritic cells. Both allogeneic effector memory (CD44(high)CD62L(low)) and central memory (CD44(high)CD62L(high)) CD8(+) T cells were identified in B6 mice with ongoing GVHD, with effector memory CD8(+) T cells as the dominant (>80%) population. Administration of these allogeneic memory CD8(+) T cells into secondary B6 recipients caused virulent GVHD. A similar allogeneic memory CD4(+) T cell population with the ability to mediate persistent GVHD was also identified in BALB/b mice receiving minor histocompatibility Ag-mismatched B6 T cell-replete bone marrow transplantation. These results indicate that allogeneic memory T cells are generated in vivo during GVH reactions and are able to cause GVHD, resulting in persistent host tissue injury. Thus, in vivo blockade of both alloreactive effector and memory T cell-mediated host tissue injury may prove to be valuable for GVHD prevention and treatment.

Skin biopsies for early diagnosis and prognosis of graft-versus-host disease in recipients of allogeneic stem cells from blood or bone marrow

A total of 61 patients with haematological malignancies were randomised either to allogeneic transplantation with blood stem cells (BSC) or bone marrow (BM), of whom 37 patients gave their consent to participate in a skin biopsy trial. Skin biopsies were performed before and after transplantation. The main objective was to assess whether biopsies of normal and affected skin from patients allografted with BSC showed a different histopathological and immunohistochemical pattern as compared to biopsies taken from patients allografted with BM. In addition, we wished to clarify whether sequential skin biopsies could be of prognostic value with regard to graft-versus-host disease (GVHD). Biopsies from normal or affected skin in BSC allografted did not disclose a different pattern as compared to BM transplants. Biopsies taken before the outbreak of acute and chronic GVHD showed no substantial differences between the groups. Irrespective of the type of allograft, the immunohistochemical picture of affected skin consistent with acute GVHD was dominated by a significantly higher number of T-lymphocytes (CD8+). Biopsies from normal skin before the outbreak of GVHD had no predictive value with regard to the development of acute or chronic GVHD. Immunohistochemistry is of supplementary help in distinguishing changes caused by cytotoxic agents from those caused by acute GVHD.

Superior depletion of alloreactive T cells from peripheral blood stem cell and umbilical cord blood grafts by the combined use of trimetrexate and interleukin-2 immunotoxin

Acute graft-versus-host disease, a major obstacle to the overall success of allogeneic hematopoietic stem cell transplantation, is primarily induced by a subset of donor T cells. Most strategies to prevent acute graft-versus-host disease target all T cells regardless of their specificity, and this leads to prolonged posttransplantation immunodeficiency. Selective depletion of alloreactive T cells could spare protective immunity and facilitate engraftment and graft-versus-leukemia effects. Recently described depletion strategies target activation markers such as CD25 that are expressed by alloreactive T cells. However, incomplete depletion may occur when a single surface epitope or pathway of apoptosis is targeted that may not be fully and concurrently expressed among all alloreactive cells. We now report on a novel strategy effective in both cord blood and peripheral blood stem cell alloreactive T cells that simultaneously induces 2 independent pathways of apoptosis after stimulation by recipient dendritic cells or Epstein-Barr virus-transformed B cells. First, we demonstrate that the folate antagonist trimetrexate selectively depletes proliferating alloreactive precursors in vitro in a dose- and time-dependent manner. Similarly, a second agent, denileukin diftitox, kills activated alloreactive T cells expressing CD25. Most importantly, these 2 agents can exert their effects in concert with superior efficacy while sparing resting bystander T cells, which remain available to mount antimicrobial or third-party responses.

Extra-domain-A fibronectin: a new marker of fibrosis in cutaneous graft-versus-host disease

One of the major complications that limit the success of allogeneic stem cell transplantation is graft-versus-host disease (GVHD). The major target organ in GVHD is the skin. Cutaneous GVHD can eventually lead to fibrosis of the skin. Fibronectin mediates a variety of cellular interactions with the extracellular matrix. The molecular and functional diversity of fibronectin (FN) arises from alternative splicing of pre-mRNA. In normal circumstances endothelial cells and fibroblasts synthesize FN without the ED-A domain. In tissue repair and pathologic circumstances such as fibrosis, the ED-A domain is expressed. We hypothesize that expression of ED-A FN is upregulated in patients with cutaneous GVHD. In frozen skin biopsies the expression of ED-A FN was measured at the protein level by immunohistochemistry and at the mRNA level by quantitative real-time PCR (qPCR). In normal control skin, immunohistochemistry showed slight deposits of ED-A FN just under the basal layer. The expression of ED-A FN significantly increased in acute cutaneous GVHD (p<0.05) and ED-A FN was strongly deposited in chronic cutaneous GVHD (p<0.001). Quantitative PCR also showed increased expression of ED-A FN mRNA in acute and chronic cutaneous GVHD compared with normal control skin (p=0.07 and 0.039, respectively). The expression of ED-A FN is increased in the skin of patients with cutaneous GVHD measured both with immunohistochemistry and qPCR. ED-A FN is a new marker of fibrosis in the skin of patients with cutaneous GVHD.

Lack of specificity in skin biopsy specimens to assess for acute graft-versus-host disease in initial 3 weeks after bone-marrow transplantation

Acute graft-versus-host disease is a serious and common complication after allogeneic bone-marrow transplantation, occurring in more than 20% of HLA antigen-identical sibling transplants and unrelated donor transplants. Bone-marrow transplantation is considered standard therapy for several hematologic malignancies and several nonhematologic disorders. In this retrospective study, we searched our institutional dermatopathology database between January 1998 and November 2002 for patients in whom skin biopsy specimens were examined less than 3 weeks after bone-marrow transplantation. A total of 40 slides from 38 patients were examined for the presence of the histologic features characteristic of acute graft-versus-host disease. Specimens of skin biopsies examined in the study varied from 3 to 21 days, with a mean of 12 days, status post-bone-marrow transplantation. The histologic findings of the 40 slides we examined were nonspecific and could be accounted for by a number of diagnoses. In summary, we propose that skin biopsies need not be preformed before 3 weeks status post-bone-marrow transplantation if the sole purpose is to rule out acute graft-versus-host disease.

APCs in the liver and spleen recruit activated allogeneic CD8+ T cells to elicit hepatic graft-versus-host disease

Host APCs are required for initiating T cell-dependent acute graft-vs-host disease (GVHD), but the role of APCs in the effector phase of acute GVHD is not known. To measure the effect of tissue-resident APCs on the local development of acute GVHD, we selectively depleted host macrophages and DCs from the livers and spleens, but not from the skin, peripheral lymph nodes (PLN), or mesenteric lymph nodes (MLN), of C57BL/6 (B6) mice by i.v. administration of liposomal clodronate before allogeneic bone marrow transplantation. Depletion of host hepatic and splenic macrophages and DCs significantly inhibited the proliferation of donor C3H.SW CD8(+) T cells in the spleen, but not in the PLN or MLN, of B6 mice. Such organ-selective depletion of host tissue APCs also markedly reduced the trafficking of allogeneic CD8(+) T cells into the livers and spleens, but not PLN and MLN, of B6 recipients compared with that of the control mice. Acute hepatic, but not cutaneous, GVHD was inhibited as well, resulting in improved survival of liposomal clodronate-treated B6 recipients. When C3H.SW CD8(+) T cells were activated in normal B6 recipients, recovered, and adoptively transferred into secondary B6 recipients, activated donor CD8(+) T cells rapidly migrated into the livers and spleens of control B6 recipients but were markedly decreased in B6 mice that were depleted of hepatic and splenic macrophages and DCs. Thus, tissue-resident APCs control the local recruitment of allo-reactive donor T cells and the subsequent development of acute GVHD.

Chronic intestinal graft-versus-host disease: clinical, histological and immunohistochemical analysis of 17 children

Graft-versus-host disease (GVHD) can be acute or chronic. The pathogenesis of chronic GVHD is unclear. Chronic GVHD affects mainly skin, liver and digestive tract. Intestinal involvement is uncommon and histological features are poorly described. We report here the clinical, histological and immunohistochemical features of chronic GVHD with intestinal involvement. Intestinal biopsies from children with chronic GVHD (n=17) were compared to control children (n=21: 10 non-transplant cases, four non-GVHD transplant cases, seven acute GVHD). We evaluated clinical outcome, histological features and characterized immunohistochemically the immune cells involved locally. Chronic GVHD with intestinal involvement was usually multisystemic (88.2%) and preceded by acute GVHD in 88.2% of cases. The outcome was severe with complete recovery in only 58.8% of cases, and death related to chronic GVHD in 17.6% of cases. Histological features were characterized by (1) villous atrophy and (2) glandular lesions, mainly apoptotic with variable intensity and (3) lamina propria infiltrate with cytotoxic T lymphocytes (CD3+, CD8+, TiA1+, granzyme B-) which were significantly (P<0.001) increased compared to non-GVHD transplant and non-transplant controls. Therefore in chronic intestinal GVHD, the apoptotic process could be related to cytotoxic T lymphocytes.

Langerhans cells and T cells in oral graft versus host disease and oral lichen planus

Chronic graft versus host disease (cGVHD) of the oral mucosa, following allogeneic stem cell transplantation, and oral lichen planus (OLP) are both mucosal diseases where the immune system is involved in the pathogenesis. Although the aetiology of the two conditions is different, they present with a similar clinical appearance. This study compares the two diseases regarding the distribution of cells, which are expressing cell surface markers of interest for inflammatory responses. Monoclonal antibodies (MoAbs) were used in standard immunohistochemical procedures. CD1a+, CD80+ and CD86+ cells in the epithelium of OLP- and cGVHD lesions had the dendritic morphology of Langerhans cells (LC). Higher frequencies of CD1a+ LC as well as CD25+ cells were observed in the OLP epithelium than in the cGVHD epithelium. The OLP lesions showed higher frequencies of subepithelial cells expressing CD1a, CD86, CD4, CD8 and CD25 than the cGVHD lesions. Notably there was a significantly higher frequency of CD25+ cells in the epithelium and the connective tissue of OLP than in cGVHD. These cells might represent regulatory T cells. In conclusion, cGVHD and OLP show marked differences at the cellular level despite similar clinical appearance. Hence, the findings indicate differences in the regulation of the inflammatory response between the two conditions.

Injection of CD4+ and CD8+ cells with donor or host accessory cells induces acute graft-vs-host disease in human skin in immunodeficient mice

OBJECTIVE

We examined cell subsets with respect to cutaneous graft-vs-host disease by cell sorting selection of subsets of human mononuclear cells and injecting the subsets subcutaneously in a mouse model.

MATERIALS AND METHODS

Cell suspensions containing cultured human epidermal cells and dermal fibroblasts from a single donor mixed with lymphoid cell subsets positively selected using the FACSVantage cell sorting instrument and/or MACS cell isolation kits from unrelated individuals were injected into immunodeficient mice. This model is known to generate human skin with histologic findings similar to human graft-vs-host disease.

RESULTS

Donor T-cell subsets CD4(+) and CD8(+) plus either host or donor CD14(+) cells were necessary to cause acute cutaneous graft-vs-host disease. Although graft-vs-host disease can result from recognition of class I antigens expressed on human cutaneous cells by donor peripheral blood mononuclear cells, additional recognition of class II antigens expressed on host mononuclear cells resulted in more severe histologic manifestations. Dendritic cells that differentiated from donor and host monocytes also showed competent accessory cell function in this system.

CONCLUSIONS

Based on this model, human cutaneous graft-vs-host disease was caused by donor CD4(+) cells and CD8(+) cells activated through recognition of host antigens, including class I and class II antigens presented by either donor or host CD14(+) cells or dendritic cells.

Determination of helper T-cell precursor frequencies against non-haemopoietic cells: comparison of co-stimulation provided by anti-CD28 antibody versus the cellular ligand B7-1

Helper T-cell precursor frequency assays (HTLp-assays) are commonly used in transplantation to examine the frequency of T cells reactive against donor or host alloantigens. In these assays, peripheral blood mononuclear cells (PBMCs) are most often used as stimulator cells. However, cells targeted after transplantation do not always belong to the haematopoietic lineage and may express different alloantigens, especially minor histocompatibility antigens (mHags). Non-haematopoietic cells lack expression of the B7 co-stimulatory molecules needed to activate primary T cells that can be supplied by anti-CD28 (alphaCD28) antibodies or transfection with B7-1 coding sequences. At present, it is not known how these two ways of supplied co-stimulation compare in HTLp assays. B7-1-transfected A431 keratinocytes (A431B7-1) induced higher proliferative responses in allogeneic primary T cells and more interleukin (IL) 2 production than that induced by A431 cells plus alphaCD28, whereas the kinetics of proliferation and IL-2 production were similar. Neither cross-linking of alphaCD28 bound to T cells nor prevention of IL-2 resorption by the anti-IL-2 receptor resulted in improved proliferation or IL-2 production. Results of HTLp assays indicated that A431B7-1 activated on average 7.5 times more alloreactive IL-2-producing T cells than A431 cells plus alphaCD28. We conclude that primary T-cell alloresponses against major histocompatibility complexes (MHCs) and mHags expressed on non-haematopoietic cells can be measured in HTLp assays using supplied co-stimulation, although alphaCD28 yields an intrinsic underestimation of actual frequencies.

Ultrastructural and functional studies of the interaction between IL-12 and IL-2 for the generation of lymphokine-activated killer cells

IL-12 promotes generation of LAK activity in short-term-cultured NK cells, but information on the structure and function of IL-12-induced LAK cells is not yet available. The latter issues have been here investigated with emphasis on interactions between IL-12 and IL-2. Peripheral blood mononuclear cells (MNC) exposed to IL-12 for 5-7 days displayed a decrease in the amount and density of the matrix of large granular lymphocyte (LGL)-associated granules. In cells cultured with IL-12 and IL-2 for 5-7 days, empty vacuoles were predominant and the electron-dense matrix was scanty. In MNC incubated with IL-2 for 5-7 days, most granules were loaded with electron-dense matrix. IL-12 and IL-2 displayed an additive effect on LAK cell cytotoxicity until approximately 48 h in culture which was followed by a sharp decline. Immunocytochemical and biochemical studies demonstrated that MNC cultured for 5-7 days with IL-12 and IL-2 displayed downregulated perforin expression and upregulated granzyme B expression. Fas ligand expression was virtually undetectable in MNC cultured for 5-7 days with or without cytokines. It appears that perforin downregulation plays a major role in the reduced cytotoxicity of MNC cultured with IL-12 and IL-2 for 5-7 days.

rC5a Directs the In Vitro Migration of Human Memory and Naive Tonsillar B Lymphocytes: Implications for B Cell Trafficking in Secondary Lymphoid Tissues

Human C5a is a potent chemoattractant for granulocytes, monocytes, and dendritic cells. In mice C5a has been shown to be chemotactic for germinal center (GC) B cells. To date, no information is available on the effects of C5a on human B cell locomotion. Here we demonstrate that rC5a increases polarization and migration of human tonsillar B cells. The locomotory response was due to both chemokinetic and chemotactic activities of rC5a. Moreover, memory and, at a lesser extent, naive B cell fractions from purified tonsillar populations displayed rC5a-enhanced migratory properties, whereas GC cells did not. Flow cytometry revealed C5aR (CD88) on approximately 40% memory and 10% naive cells, respectively, whereas GC cells were negative. Immunohistochemistry showed that a few CD88+ cells were of the B cell lineage and localized in tonsillar subepithelial areas, where the majority of memory B cells settle. Pretreatment of memory B cells with the CD88 mAb abolished their migratory responsiveness to rC5a. Finally, the C5 gene was found to be expressed in naive, GC, and memory B lymphocytes at both the mRNA and the protein level. This study delineates a novel role for C5a as a regulator of the trafficking of human memory and naive B lymphocytes and supports the hypothesis that the B cells themselves may serve as source of C5 in secondary lymphoid tissues.

Effect of FLT3 Ligand and Granulocyte Colony-Stimulating Factor on Expansion and Mobilization of Facilitating Cells and Hematopoietic Stem Cells in Mice: Kinetics and Repopulating Potential

We have previously identified a cellular population in murine bone marrow that facilitates engraftment of highly purified hematopoietic stem cells (HSC) across major histocompatibility complex (MHC) barriers without causing graft-versus-host disease. Here we investigated the effect of flt3 ligand (FL) and granulocyte colony-stimulating factor (G-CSF) on the mobilization of facilitating cells (FC) and HSC into peripheral blood (PB). Mice were injected with FL alone (day 1 to 10), G-CSF alone (day 4 to 10), or both in combination. The number of FC (CD8+/βTCR−/γδTCR−) and HSC (lineage−/Sca-1+/c-kit+) was assessed daily by flow cytometry. Lethally irradiated allogeneic mice were reconstituted with PB mononuclear cells (PBMC). FL and G-CSF showed a highly significant synergy on the mobilization of FC and HSC. The peak efficiency for mobilization of FC (21-fold increase) and HSC (200-fold increase) was reached on day 10. Our data further suggest that the proliferation of FC and HSC induced by FL in addition to the mobilizing effect mediated by G-CSF might be responsible for the observed synergy of both growth factors. Finally, the engraftment potential of PBMC mobilized with FL and G-CSF or FL alone was superior to PBMC obtained from animals treated with G-CSF alone. Experiments comparing the engraftment potential of day 7 and day 10 mobilized PBMC indicate that day 10, during which both FC and HSC reached their maximum, might be the ideal time point for the collection of both populations. © 1998 by The American Society of Hematology.

Effect of FLT3 Ligand and Granulocyte Colony-Stimulating Factor on Expansion and Mobilization of Facilitating Cells and Hematopoietic Stem Cells in Mice: Kinetics and Repopulating Potential

We have previously identified a cellular population in murine bone marrow that facilitates engraftment of highly purified hematopoietic stem cells (HSC) across major histocompatibility complex (MHC) barriers without causing graft-versus-host disease. Here we investigated the effect of flt3 ligand (FL) and granulocyte colony-stimulating factor (G-CSF) on the mobilization of facilitating cells (FC) and HSC into peripheral blood (PB). Mice were injected with FL alone (day 1 to 10), G-CSF alone (day 4 to 10), or both in combination. The number of FC (CD8+/βTCR−/γδTCR−) and HSC (lineage−/Sca-1+/c-kit+) was assessed daily by flow cytometry. Lethally irradiated allogeneic mice were reconstituted with PB mononuclear cells (PBMC). FL and G-CSF showed a highly significant synergy on the mobilization of FC and HSC. The peak efficiency for mobilization of FC (21-fold increase) and HSC (200-fold increase) was reached on day 10. Our data further suggest that the proliferation of FC and HSC induced by FL in addition to the mobilizing effect mediated by G-CSF might be responsible for the observed synergy of both growth factors. Finally, the engraftment potential of PBMC mobilized with FL and G-CSF or FL alone was superior to PBMC obtained from animals treated with G-CSF alone. Experiments comparing the engraftment potential of day 7 and day 10 mobilized PBMC indicate that day 10, during which both FC and HSC reached their maximum, might be the ideal time point for the collection of both populations. © 1998 by The American Society of Hematology.