Engraftment Of Human Lymphocytes Research Articles

Humanization with CD34-positive hematopoietic stem cells in NOG-EXL mice results in improved long-term survival and less severe myeloid cell hyperactivation phenotype relative to NSG-SGM3 mice.

NSG-SGM3 and NOG-EXL mice combine severe immunodeficiency with transgenic expression of human myeloid stimulatory cytokines, resulting in marked expansion of myeloid populations upon humanization with CD34+ hematopoietic stem cells (HSCs). Humanized NSG-SGM3 mice typically develop a lethal macrophage activation syndrome and mast cell hyperplasia that limit their use in long-term studies (e.g., humanization followed by tumor xenotransplantation). It is currently unclear to what extent humanized NOG-EXL mice suffer from the same condition observed in humanized NSG-SGM3 mice. We compared the effects of human CD34+ HSC engraftment in these two strains in an orthotopic patient-derived glioblastoma model. NSG-SGM3 mice humanized in-house were compared to NOG-EXL mice humanized in-house and commercially available humanized NOG-EXL mice. Mice were euthanized at humane or study endpoints, and complete pathological assessments were performed. A semiquantitative multiparametric clinicopathological scoring system was developed to characterize chimeric myeloid cell hyperactivation (MCH) syndrome. NSG-SGM3 mice were euthanized at 16 weeks after humanization because of severe deterioration of clinical conditions. Humanized NOG-EXL mice survived to the study endpoint at 22 weeks after humanization and showed less-severe MCH phenotypes than NSG-SGM3 mice. Major differences included the lack of mast cell expansion and limited tissue/organ involvement in NOG-EXL mice compared to NSG-SGM3 mice. Engraftment of human lymphocytes, assessed by immunohistochemistry, was similar in the two strains. The longer survival and decreased MCH phenotype severity in NOG-EXL mice enabled their use in a tumor xenotransplantation study. The NOG-EXL model is better suited than the NSG-SGM3 model for immuno-oncology studies requiring long-term survival after humanization.

Prevention of acute graft‐versus‐host disease by humanized anti‐CD26 monoclonal antibody

CD26 (DPP4) is a T cell costimulatory molecule as well as T cell activation marker, and CD26(+) T cells are accumulated in inflamed tissues, such as rheumatoid synovitis and autoimmune thyroiditis. In the present study, we found accumulation of CD26(+) T cells in graft-versus-host disease (GVHD) target organs. To expand our in vitro findings to an in vivo system, we examined CD26-dependent organ injury in a xenogeneic GVHD (x-GVHD) murine model. Following intraperitoneal injection of human peripheral blood mononuclear cells into non-obese diabetic severe combined immunodeficiency/γ(c) (-/-) mice (hu-PBL-NOG mice), the mice exhibited the onset of GVHD symptoms associated with the presence of CD26(high) human lymphocytes in the peripheral blood and GVHD target tissues. Administration of humanized anti-human CD26 monoclonal antibody (mAb) decreased x-GVHD severity and prolonged survival in hu-PBL-NOG mice without loss of engraftment of human T cells, while increasing doses of CTLA4- immunoglobulin fusion protein diminished engraftment of human lymphocytes. Importantly, anti-CD26 mAb treatment preserved the graft-versus-leukaemia effects in studies using cotransplantation of P815 murine leukaemic cells. In addition, CD26(+) lymphocytes infiltrated the GVHD patients' target tissues. Altogether, our data indicate a role for CD26 in the regulation of GVHD and point to CD26 as a novel target for therapeutic intervention in this disease.

Restoration of skeletal muscle ischemia-reperfusion injury in humanized immunodeficient mice

Ischemia and reperfusion (I/R) of tissue provokes an inflammatory process that is highly dependent on circulating natural immunoglobulin M (IgM) and the complement cascade. In mice, a single IgM specificity produced by peritoneal B cells can initiate reperfusion injury. It is unknown whether humans express natural IgM with a similar specificity. It is also unknown whether pathogenic IgM is produced solely from peritoneal B cells or can also be made by circulating B cells. Immunodeficient mice lacking endogenous immunoglobulin were used. Mice were reconstituted with 0.9% normal saline, human serum, or xenografted human peripheral blood lymphocytes (PBLs) and then subjected to tourniquet-induced hindlimb I/R. Serum human IgM and immunoglobulin G (IgG) were measured by enzyme-linked immunosorbent (ELISA) assay. Skeletal muscle was harvested for injury assessment by histology and for immunohistochemistry. Immunodeficient mice were protected from skeletal muscle injury after hindlimb I/R. Transfer of human serum restored skeletal muscle damage. Rag2/gammaR-/- mice that were engrafted with human PBL (huPBL-SCID) had high levels of human IgM. huPBL-SCID mice developed significantly more skeletal muscle injury than control saline-treated mice (P < or = .01) and human serum-reconstituted Rag2/gammaR-/- mice (P < or = 0.01). Sham-treated huPBL-SCID mice had no muscle injury, demonstrating that human lymphocyte engraftment did not cause injury in the absence of ischemia. Deposition of human IgM was observed on injured but not sham-injured muscle. Human serum can initiate murine skeletal muscle I/R injury. Circulating human PBL may be a source of pathogenic IgM. The huPBL-SCID mouse may be a useful model to define the specificity of pathogenic human IgM and to test therapeutics for I/R injury.

Alcohol Abuse Enhances Neuroinflammation and Impairs Immune Responses in an Animal Model of Human Immunodeficiency Virus-1 Encephalitis

Neuroinflammatory disorders (including human immunodeficiency virus-1 encephalitis, HIVE) are associated with oxidative stress and inflammatory brain injury, and excessive alcohol use can exacerbate tissue damage. Using a murine model of HIVE, we investigated the effects of alcohol abuse on the clearance of virus-infected macrophages and neuroinflammation. Severe combined immunodeficient mice were reconstituted with human lymphocytes, and encephalitis was induced by intracranial injection of HIV-1-infected monocyte-derived macrophages (HIV-1(+) MDM). Animals were fed an ethanol-containing diet beginning 2 weeks before lymphocyte engraftment and for the entire duration of the experiment. Lymphocyte engraftment was not altered by ethanol exposure. Alcohol-mediated immunosuppression in ethanol-fed mice was manifested by a significant decrease in CD8(+)/interferon-gamma(+) T lymphocytes, a fivefold increase in viremia, and diminished expression of immunoproteasomes in the spleen. Although both groups showed similar amounts of CD8(+) T-lymphocyte infiltration in brain areas containing HIV-1(+) MDMs, ethanol-fed mice featured double the amounts of HIV-1(+) MDMs in the brain compared to controls. Ethanol-exposed mice demonstrated higher microglial reaction and enhanced oxidative stress. Alcohol exposure impaired immune responses (increased viremia, decreased immunoproteasome levels, and prevented efficient elimination of HIV-1(+) MDMs) and enhanced neuroinflammation in HIVE mice. Thus, alcohol abuse could be a co-factor in progression of HIV-1 infection of the brain.

Engraftment of human T, B and NK cells in CB.17 SCID/beige mice by transfer of human spleen cells

Models of severe combined immuno-deficient (SCID) mice reconstituted with a competent human immune system represent a valuable tool for the study of human immune responses in vivo. Reconstitution with human cells can be achieved using large numbers of peripheral blood lymphocytes, but levels of engraftment are poor and graft versus host disease (GVHD) frequently occurs. SCID/beige mice are at the same time deficient for adaptive and innate immunity and the objective of this study was to develop a safe and efficient way to achieve human lymphocyte engraftment in these mice using human spleen cells. After institutional authorisations and informed consent of relatives, a piece of spleen was obtained from cadaveric organ donors and the splenocytes were isolated and cryopreserved for later use. Single intraperitoneal injections of 5–100 × 10 6 splenocytes were performed into SCID/beige mice. Reconstitution of a human immune system was monitored weekly by the presence of human cells and IgG in peripheral blood. The mice were sacrificed 4 weeks after the injection and the engraftment in lymphoid organs was studied. A reproducible reconstitution was obtained with intraperitoneal injection of 30–40 × 10 6 spleen cells. Human T, B and NK cells as well as human IgG were present in peripheral blood. In lymphoid tissues, the same lymphocytic subpopulations were detected and in addition some antigen presenting cells. The reconstitution was functional because graft rejection was observed after transplantation of human allogeneic tissues. When less than 30 × 10 6 cells were injected, the reconstitution was variable. When more than 40 × 10 6 cells were injected, GVHD occurred with increasing frequency. In conclusion, we show that intraperitoneal injection of 30–40 × 10 6 human splenocytes into SCID/beige mice induces a quick and functional engraftment of human T, B and NK cells with no risk of GVHD. This model may be used to study human transplantation immunobiology in vivo.

Effects of human interleukin-18 and interleukin-12 treatment on human lymphocyte engraftment in NOD-scid mouse.

NOD/LtSz-prkdc(scid)/prkdc(scid) (non-obese diabetic-severe combine immunodeficiency; NOD-scid) mice grafted with human peripheral blood lymphoid cells have been used as an in vivo humanized mouse model in various studies. However, cytotoxic human T cells are induced in this model during immune responses, which gives misleading results. To assist in grafting of human lymphocytes without the induction of cytotoxic human T cells, we investigated the effects of T helper type 1 (Th1) and Th2 cytokines on human lymphocyte grafting and migration, as well as the production of immunoglobulin deposited in glomeruli and human immunodeficiency virus-1 (HIV-1) infection using NOD-scid mice. Administration of interleukin-18 (IL-18) and IL-12 enhanced the grafting of human CD4+ and CD8+ T cells in the mice, whereas co-administration prevented grafting due to interferon-gamma-dependent apoptosis. Immunoglobulin A (IgA) deposits were observed in mice treated with IL-18 alone, but not in those given phosphate-buffered saline, IL-12 alone, or IL-18 + IL-12. A high rate of HIV infection was also observed in the IL-18-treated group. Together, these results indicate that IL-18 may be effective for the grafting and migration of CD4+ and CD8+ T cells, except for the induction of apoptosis and regulation of class-switching IgA. IL-18-administered NOD-scid mice provide a useful small humanized model for the study of HIV infection and IgA nephropathy.

Molecular analysis of the heavy chain of antibodies that recognize the capsular polysaccharide of Neisseria meningitidis in hu-PBMC reconstituted SCID mice and in the immunized human donor

The severe combined immunodeficient (SCID) mouse model, engrafted with human peripheral blood mononuclear cells (hu-PBMC) has proven to be useful in studying the human immune response. A major limitation of the hu-PBMC-SCID model has been the failure to consistently demonstrate a primary human immune response. Previously we developed a hu-PBMC-SCID mouse model in which we addressed both issues of adequate human lymphocyte engraftment and impaired differentiation. We demonstrated that a primary human immune response to the T-independent (TI-2) meningococcal group C capsular polysaccharide (MCPS) can be obtained in hu-PBMC-SCID mice by the administration of human cytokines. In this study we compared the V H sequence of the MCPS response generated by B cells derived from a volunteer in the SCID mouse model to those generated by the donors’ B cells in vivo. Human peripheral blood mononuclear cells were recovered from MCPS immunized hu-PBMC-SCID mice and immunized donor. B cells with specificity for MCPS were isolated from these cell preparations using an anti-idiotypic monoclonal antibody which mimics MCPS. Immunoglobulin mRNA was isolated from single cells, amplified by the polymerase chain reaction, cloned and sequenced. We analysed a total of 15 V H regions from B cells obtained from SCID mice and a total of 13 V H regions from B cells obtained from the immunized donor. The response differed between SCID and in vivo cells, when studied at the genetric level. V, D and J gene usage was markedly different, however canonical structures of the hypervariable loops were conserved. The complementary determining region 3 (CDR3) varied, such that SCID-derived sequences encoded longer CDR3 s than those of the donor. However all CDR3 s were rich in hydrophobic amino acids, most notably tyrosine and tryptophan, a characteristic common to many carbohydrate binding antibodies.

Human IL-6 Enhances Human Lymphocyte Engraftment and Activation but not Human Antibody Production in SCIDhu PBL Mice

The SCIDhu PBL model of human Ig production was modified by using human interleukin-6 (hIL-6) secreting tumors for continuous hIL-6 production, in vivo. On day one, SCID mice were injected subcutaneously with 200 µl PBS (control mice), 10 4 SP2/0-Ag14 cells (IL-6 − mice) or 10 4 hIL-6 secreting SP2/0-hIL6.17 cells (IL-6 + mice). The mice were reconstituted with human PBMC on day two and immunized with 100 µg of tetanus toxoid (TT) on days two and fifteen. Serum hIL-6 concentrations in IL-6 + mice ranged between 2.9 and 38.1 ng/ml by days 26−33. IL-6 + mice had enlarged spleens and lymph nodes (LN). Flow cytometry and histology showed that SCIDhu PBL mouse spleen, LN and peritoneal exudate cells (PEC) contained mostly murine myeloid lineage cells. In addition, many more human B cells, T cells and IL-2R +-activated lymphocytes were present in spleen, LN and PEC of IL-6 + mice. Despite enhanced lymphocyte engraftment and activation, by day 14 IL-6 + mice produced up to 6-fold less TT-specific IgG relative to total IgG than either control group. TT-specific and total Ig sera concentrations were equivalent in all three groups on days 26–33. Our results suggest that sustained circulating hIL-6 enhanced human delayed-type hypersensitivity (DTH)-like inflammatory responses with consequential inhibition of TT-specific IgG production in SCIDhu PBL mice.

A lymphocyte-activating monoclonal antibody induces regression of human tumors in severe combined immunodeficient mice.

Monoclonal antibodies were raised against Daudi B-lymphoblastoid cell line membranes. An mAb (BAT) was selected for its ability to stimulate human and murine lymphocyte proliferation. BAT induced cytotoxicity in human and murine lymphocytes against natural killer cell-sensitive and -resistant tumor cell lines. A single intravenous administration of BAT to mice that had been inoculated with various murine tumors (e.g., B16 melanoma, 3LL carcinoma, and methylcholanthrene fibrosarcoma) resulted in striking antitumor effects as manifested by complete tumor regression and prolonged survival of the treated mice. BAT exhibited a diminished but significant antitumor effect in athymic nude mice, which are deficient in T lymphocytes, and in beige mice, which are deficient in NK cells. Furthermore, selective depletion of T or NK cells in mice reduced the response to the antitumor effect of BAT. These data indicate a dual role for T and NK cells in mediating the antitumor activity of BAT. We report here on the antitumor activity of BAT mAb on human tumor xenografts in mice. BAT demonstrated an antitumor effect in nude mice bearing human colon carcinoma (HT29) xenografts. It failed, however, to inhibit established lung metastases in severe combined immunodeficient (SCID) mice that had been inoculated (i.v.) with SK28 human melanoma. Engraftment of human lymphocytes into SCID mice bearing human melanoma xenografts rendered them responsive to the antitumor effect of BAT. The efficacy of BAT in the regression of human tumors by activation of human lymphocytes indicates its potential clinical use.

Evidence for restricted diversity of antigen-specific human antibodies in immunized hu-PBL-SCID mice

Previous studies have revealed that specific human humoral immune responses could be produced in immunized SCID mice after engraftment of human lymphocytes (hu-PBL-SCID). On the other hand, the engrafted repertoire of B cell clones is known to be skewed in hu-PBL-SCID with the corresponding production of only a limited set of major human antibodies. In this work, we have analyzed the diversity of tetanus toxoid-specific human antibodies produced in immunized hu-PBL-SCID mice in comparison with the total serum antibody population using zone electrophoresis followed by blotting. The results showed that the diversity of tetanus toxoid-specific antibody population was more restricted than that of the total human antibody population, with some animal sera containing a single band of tetanus toxoid-specific antibody molecule, in clear contrast to the polyclonal response of the PBL donor. Absorption experiments showed tetanus toxoid-specific antibodies could account for a significant proportion (up to 10%) of the total human antibodies present in hu-PBL-SCID mouse sera. The inability to expand a high number of different antigen-specific B cell clones in immunized hu-PBL-SCID mice represents an important intrinsic limitation of this animal model which may be caused by defects in T cell help.

Anti-SCID mouse reactivity shapes the human CD4+ T cell repertoire in hu-PBL-SCID chimeras.

Injecting human peripheral blood mononuclear cells into severe combined immunodeficient (SCID) mice results in long-term engraftment of human lymphocytes, of which > 98% are phenotypically mature, activated T cells. Here we have characterized the human T cells that populate such hu-PBL-SCID chimeras. We report that these human T cells do not mobilize Ca2+ after CD3 stimulation, i.e., their T cell receptor (TCR)-mediated signal transduction is deficient. Chimera-derived human T cells do not secrete lymphokines or undergo blastogenesis after CD3 stimulation, but proliferate in response to interleukin 2 (IL-2), defining the chimera derived human T cells as anergic. Anergy was seen in both the CD4+ and the CD8+ subpopulations. We established human T cell lines from chimeras. These T cells retained their anergic state for 1-2 mo in culture, after which they simultaneously regained the ability to mobilize Ca2+, secrete lymphokines, and to undergo blastogenesis following stimulation via the TCR. Once regaining proliferative responsiveness to CD3 stimulation, these CD4+ T cell lines displayed anti-SCID mouse reactivity and showed no specificity for recall antigens. All CD3-responsive CD4+ T cell clones obtained from such lines were SCID mouse specific, recognizing native major histocompatibility complex class II products on the murine cells. In contrast, chimera-derived human CD8+ cell lines and clones did not display detectable anti-mouse reactivity. The data show that the human T cell system in long term hu-PBL-SCID chimeras is nonfunctional due to both anergy and the limitation of the CD4+ repertoire to xenoreactive clones. The data suggest that long-term hu-PBL-SCID chimerism represents an atypical graft-versus-host reaction in which the human effector T cells become anergic in the murine environment.

Engraftment of human lymphocytes and thyroid tissue into scid and rag2- deficient mice: absent progression of lymphocytic infiltration

Engraftment of human lymphocytes and thyroid tissue into scid and rag2- deficient mice: absent progression of lymphocytic infiltration

Engraftment of human lymphocytes and thyroid tissue into scid and rag2-deficient mice: absent progression of lymphocytic infiltration.

To study human autoimmune thyroid disease in an animal model we have investigated the in vivo survival of human thyroid tissues and functionality of human lymphocytes in severe combined immunodeficient (scid) mice and recombination-activating gene (rag2) knockout mice. We found successful engraftment of human thyroid tissues in both scid and rag2-deficient mice. However, when peripheral blood mononuclear cells were transplanted ip, human immunoglobulin production was poor in rag2-deficient mice compared to that in scid mice (mean human immunoglobulin G levels at 6 weeks, 0.2 +/- 0.2 microgram/mL in two of eight rag2-deficient mice compared to 20.8 +/- 7.0 micrograms/mL in seven of nine scid mice; P < 0.05). We, therefore, only pursued the further use of scid mice and transplanted them with thyroid tissue from patients with either Graves' disease (four patients) or Hashimoto's thyroiditis (one patient). At the functional level, we observed transiently increased thyroid hormone levels (T4 peaking at 5.4 +/- 0.2 microgram/dL compared to a normal level of 2.6 +/- 0.2 microgram/dL); human autoantibodies to human thyroglobulin, human thyroid peroxidase, and the human TSH receptor were also detected in thyroid-transplanted mice. In contrast to recent reports, histological examination of the thyroid explants showed no increase in the lymphocytic infiltrate compared to the original donor tissue, nor was there any thyroid follicular destruction observed. In fact, many of the transplants demonstrated a marked diminution in the infiltrates over time, with an absence of HLA-DR antigen expression by both T-cells and thyrocytes. Cotransplanted allogeneic thyroid tissues were unremarkable in terms of lymphocytic infiltrates and showed intact morphology. Taken together, these data point to a relative degree of T-cell inactivity within the thyroid explants from the scid mouse. Hence, a factor(s) present in the patient with autoimmune thyroid disease that activates their thyroid-specific T-cells may be absent in this murine model as presently constructed.

Recombinant human growth hormone promotes human lymphocyte engraftment in immunodeficient mice and results in an increased incidence of human Epstein Barr virus-induced B-cell lymphoma

Recombinant human growth hormone (rhGH) previously has been demonstrated to promote human or mouse T-cell engraftment in immunodeficient mice. We then wanted to examine long-term effects of rhGH on human cell engraftment in these mice. Mice with severe combined immune deficiency (SCID) were given human peripheral blood lymphocytes or human bone marrow cells and daily injections of rhGH (20 μg ip every other day). Upon later assessment for engraftment by flow cytometric analysis, it was determined that rhGH strongly promoted human T-cell engraftment in the thymus and spleens of these mice. However, there was considerable variability in both the incidence and extent of engraftment which appears to be due to donor-to-donor variation. Additionally, rhGH promoted B lymphomagenesis in these mice since long-term treatment of these xenogeneic chimeras with rhGH resulted in the increased incidence of human Epstein-Barr virus (EBV)-infected B-cell lymphoma. Thus, while rhGH can be used to optimize human T-cell engraftment in SCID mice, it also increases the likelihood of B-cell lymphoma generation when the donor is EBV infected. The results suggest that the activation of human T cells by rhGH results in an increased ability of these cells to traffic to the peripheral lymphoid organs of the SCID mice and results in a lymphoid microenvironment conductive to the outgrowth of EBV-transformed B lymphocytes.

Human-mouse lymphoid chimeras: host-vs.-graft and graft-vs.-host reactions.

Human peripheral blood lymphocytes (huPBL) were injected into mice with severe combined immune deficiency (SCID). It was ascertained that murine natural killer (NK) cells were capable of affecting engraftment of human lymphocytes in SCID mice. The presence of host NK cells resulted in the clearance of the human lymphocytes. Human T lymphocytes were the primary cell to engraft in the SCID recipients, with human T cells being detected in the spleen, lymph nodes, bone marrow and peritoneal cavity of the mice up to several months after transfer. No human T cells were detected in the murine thymus and the level of engraftment in the periphery could be highly variable. Additionally, there appeared to be significant reactions between the human lymphocytes and the murine host resulting in a xenogeneic graft-vs.-host reaction (XGVHR). The predominant manifestation involved splenomegaly resulting from an expansion of murine hematopoietic cells in the spleens of these xenogeneic chimeras. The severity of the XGVHR could be correlated with the extent of human T cell engraftment and the recovered human T cells were found to be in a proliferative state. Thus, there appear to be significant host-vs.-graft and graft-vs.-host interactions occurring in human/mouse lymphocyte chimeras.

Acute human vs. mouse graft vs. host disease in normal and immunodeficient mice

Recent reports of persistent engraftment of human lymphocytes and myeloid cells in hereditary immunodeficient severe combined immunodeficient mice (SCID) and beige athymic nude X-linked immunodeficiency (Bg/Nu/XID) mice have raised the question of why attempts to graft human cells into artificially immunosuppressed normal mice have failed so far. In the present study we provide evidence that this difference is due to the absence of natural antibodies in the mutant mice. We demonstrate that human PBL can be grafted in normal mice immunosuppressed by heavy doses of total body irradiation, provided the transplant is performed when the recipients lack natural antibodies in their serum, e.g. as in newborn normal mice, in mice treated with anti-mouse IgM antibody from birth, and in 3-week-old B cell-deficient CBA/N mice. In all cases, large numbers of human PBL were required. Under these conditions an acute and fatal graft vs. host disease (GVHD) developed in the recipients, regardless of whether these were artificially immunosuppressed or hereditary immunodeficient. The clinical manifestations and the histopathology of this xenogeneic acute GVHD are quite different from those of allogeneic GVHD. The former is primarily confined to the hematolymphoid tissues and locations close to accumulations of proliferating lymphoblasts, such as the peritoneal cavity in case of i.p. transplantation. The discordant xenogeneic GVHD is induced by human T lymphocytes and can be abrogated by treatment with anti-human T cell serum.

Distribution and engraftment patterns of human tonsillar mononuclear cells and immunoglobulin-secreting cells in mice with severe combined immunodeficiency: role of the Epstein-Barr virus.

Tonsils seem to be the ideal source of lymphocytes seeding to the mucosa of the respiratory tract. The distribution and engraftment of human lymphocytes injected into mice with severe combined immunodeficiency (SCID) are not well understood. C.B-17 SCID mice were injected intraperitoneally with human tonsillar mononuclear cells (hu-TMC). The hu-TMC-SCID mouse chimeras were subsequently tested for the appearance and distribution of human lymphocytes tagged with H33342 and immunoglobulin-secreting cells in various systemic and mucosal immunocompetent tissues. This was done by fluorescence microscopy of tissue sections for cells supravitally stained before transfer and by an enzyme-linked immunospot assay using cells isolated from murine organs. Most importantly, engraftment of hu-TMC proved to be dependent on the presence of anti-Epstein-Barr virus (EBV) antibody in the donor. hu-TMC engrafted, in decreasing numbers, in the following systemic organs: peritoneal cavity, liver, spleen and bone marrow. Among mucosal tissues tested, hu-TMC were seen in lungs, but not in the intestines. The engraftment of hu-TMC in the lung was more extensive than that in the spleen. These studies demonstrate that hu-TMC engraft in a variety of murine tissues. The striking preference of hu-TMC for the lungs when compared to intestines suggests selective engraftment among distinct mucosal tissues. The hu-TMC-SCID mouse chimera promises to be a unique animal model to study human-mucosa-associated lymphoid cells and EBV-related lymphomagenesis and B cell tumor progression.