The cellular composition of human lymph nodes after allogenic bone marrow transplantation: an immunohistological study

Graft-versus-host disease reduces lymph node display of tissue-restricted self-antigens and promotes autoimmunity

Acute graft-versus-host disease (GVHD) is initially triggered by alloreactive T cells, which damage peripheral tissues and lymphoid organs. Subsequent transition to chronic GVHD involves the emergence of autoimmunity, although the underlying mechanisms driving this process are unclear. Here, we tested the hypothesis that acute GVHD blocks peripheral tolerance of autoreactive T cells by impairing lymph node (LN) display of peripheral tissue–restricted antigens (PTAs). At the initiation of GVHD, LN fibroblastic reticular cells (FRCs) rapidly reduced expression of genes regulated by DEAF1, an autoimmune regulator-like transcription factor required for intranodal expression of PTAs. Subsequently, GVHD led to the selective elimination of the FRC population, and blocked the repair pathways required for its regeneration. We used a transgenic mouse model to show that the loss of presentation of an intestinal PTA by FRCs during GVHD resulted in the activation of autoaggressive T cells and gut injury. Finally, we show that FRCs normally expressed a unique PTA gene signature that was highly enriched for genes expressed in the target organs affected by chronic GVHD. In conclusion, acute GVHD damages and prevents repair of the FRC network, thus disabling an essential platform for purging autoreactive T cells from the repertoire.

Learning from other autoimmunities to understand targeting of B cells to control multiple sclerosis

Although many suspected autoimmune diseases are thought to be T cell-mediated, the response to therapy indicates that depletion of B cells consistently inhibits disease activity. In multiple sclerosis, it appears that disease suppression is associated with the long-term reduction of memory B cells, which serves as a biomarker for disease activity in many other CD20+ B cell depletion-sensitive, autoimmune diseases. Following B cell depletion, the rapid repopulation by transitional (immature) and naïve (mature) B cells from the bone marrow masks the marked depletion and slow repopulation of lymphoid tissue-derived, memory B cells. This can provide long-term protection from a short treatment cycle. It seems that memory B cells, possibly via T cell stimulation, drive relapsing disease. However, their sequestration in ectopic follicles and the chronic activity of B cells and plasma cells in the central nervous system may drive progressive neurodegeneration directly via antigen-specific mechanisms or indirectly via glial-dependent mechanisms. While unproven, Epstein-Barr virus may be an aetiological trigger of multiple sclerosis. This infects mature B cells, drives the production of memory B cells and possibly provides co-stimulatory signals promoting T cell-independent activation that breaks immune tolerance to generate autoreactivity. Thus, a memory B cell centric mechanism can integrate: potential aetiology, genetics, pathology and response to therapy in multiple sclerosis and other autoimmune conditions with ectopic B cell activation that are responsive to memory B cell-depleting strategies.

Foreign Body Granuloma: A New Manifestation of Immune Restoration Syndrome

Background:

People with human immunodeficiency virus may experience an immune restoration syndrome during the lymphocyte recovery period following effective highly active antiretroviral therapy. In this syndrome, antigens that previously were ignored by the immune system now induce an exaggerated response with obvious clinical effects. Most cases have been associated with infectious agents such as cytomegalovirus or mycobacterium avium intracellulare. However, the sudden onset of sarcoidal granulomatous reactions have also been described in this setting.

Objective:

We report a 66-year-old HIV-positive man who presented with exacerbation of multiple foreign body granulomas decades after the original injuries. The presentation coincided with a significant rise in CD4 count after beginning highly active antiretroviral therapy.

Conclusion:

We propose that this case demonstrates another manifestation of the immune restoration syndrome and postulate that an uncontrolled Th1 response is the causative mechanism.

Reconstitution of the immune system after hematopoietic stem cell transplantation in humans

Hematopoietic stem cell transplantation is associated with a severe immune deficiency. As a result, the patient is at high risk of infections. Innate immunity, including epithelial barriers, monocytes, granulocytes, and NK cells recovers within weeks after transplantation. By contrast, adaptive immunity recovers much slower. B- and T-cell counts normalize during the first months after transplantation, but in particular, T-cell immunity may remain impaired for years. During the last decade, much of the underlying mechanisms have been identified. These insights may provide new therapies to accelerate recovery.

Aberrant regulation of superantigen responses during T-cell reconstitution and graft-versus-host disease in immunodeficient mice

Acute graft-versus-host disease (GVHD) after allogeneic stem cell transplantation is associated with impaired deletion and anergy of host-reactive T cells. To elucidate the immunoregulatory events that may contribute to such dysregulated T-cell responses in GVHD, we studied superantigen (SAg) responses after adoptive T-cell transfer into severe combined immunodeficient (SCID) mice. SAg responses are normally regulated by mechanisms involving deletion and anergy, with SAg-reactive T cells typically being deleted rapidly in vivo. In a SCID mouse model of GVHD, however, allogeneic host SAg-reactive T cells were not deleted rapidly, but rather persisted in increased numbers for several months. Moreover, depending on the timing of SAg stimulation and the numbers of T cells transferred, dysregulation (impaired deletion and anergy) of SAg responses could be demonstrated following the adoptive transfer of syngeneic T cells into SCID mice as well. Transgenic T-cell receptor-bearing KJ1-26.1+ T cells were then used to determine the fate of weakly reactive T cells after adoptive transfer and SAg stimulation. When transferred alone, KJ1-26.1+ T cells demonstrated impaired deletion and anergy. In the presence of more strongly staphylococcal enterotoxin B (SEB)–reactive T cells, however, KJ1-26.1+ T cells were regulated normally, in a manner that could be prevented by inhibiting the effects of more strongly SEB-reactive cells or by increasing the level of activation of the KJ1-26.1+ T cells themselves. We suggest that the control mechanisms that normally regulate strongly activated T cells in immunocompetent animals are lost following adoptive transfer into immunodeficient hosts, and that this impairment contributes to the development of GVHD.

Aberrant regulation of superantigen responses during T-cell reconstitution and graft-versus-host disease in immunodeficient mice

Acute graft-versus-host disease (GVHD) after allogeneic stem cell transplantation is associated with impaired deletion and anergy of host-reactive T cells. To elucidate the immunoregulatory events that may contribute to such dysregulated T-cell responses in GVHD, we studied superantigen (SAg) responses after adoptive T-cell transfer into severe combined immunodeficient (SCID) mice. SAg responses are normally regulated by mechanisms involving deletion and anergy, with SAg-reactive T cells typically being deleted rapidly in vivo. In a SCID mouse model of GVHD, however, allogeneic host SAg-reactive T cells were not deleted rapidly, but rather persisted in increased numbers for several months. Moreover, depending on the timing of SAg stimulation and the numbers of T cells transferred, dysregulation (impaired deletion and anergy) of SAg responses could be demonstrated following the adoptive transfer of syngeneic T cells into SCID mice as well. Transgenic T-cell receptor-bearing KJ1-26.1+ T cells were then used to determine the fate of weakly reactive T cells after adoptive transfer and SAg stimulation. When transferred alone, KJ1-26.1+ T cells demonstrated impaired deletion and anergy. In the presence of more strongly staphylococcal enterotoxin B (SEB)–reactive T cells, however, KJ1-26.1+ T cells were regulated normally, in a manner that could be prevented by inhibiting the effects of more strongly SEB-reactive cells or by increasing the level of activation of the KJ1-26.1+ T cells themselves. We suggest that the control mechanisms that normally regulate strongly activated T cells in immunocompetent animals are lost following adoptive transfer into immunodeficient hosts, and that this impairment contributes to the development of GVHD.

Long-term persistence of IL-2-unresponsive allogeneic T cells in sublethally irradiated SCID mice

Donor T cells that are activated by host alloantigens initiate graft versus host disease (GVHD) but their long-term fate is poorly understood. The behavior of alloreactive donor T cells was studied in sublethally irradiated SCID mice. Intravenous injection of 10(6) allogeneic lymphocytes caused a severe form of GVHD, characterized by host hematopoietic atrophy. Fifty-fold fewer donor cells did not induce disease and were not simply rejected by radioresistant host mechanisms. Instead, low numbers of allogeneic T cells expanded 20- to 50-fold and remained for >1 year without causing evidence of GVHD. Persistent non-cycling donor cells with an activated phenotype were mainly found in the spleen. Tolerance was inferred by the recovery of host hematopoiesis, despite the presence of donor allogeneic T cells, and the inability of long-term persisting donor T cells to mediate cellular cytotoxicity or proliferate in response to exogenous IL-2 or antigenic stimulation in vitro. The TCR density of long-term persisting donor T cells was down-regulated. These findings suggest that the development of GVHD depends on the magnitude of the initial anti-host response. Subsequently donor cells differentiate, over several months, into a senescent-like state. This behavior questions the rationale for current treatment approaches to GVHD and is of relevance to any clinical situation where chronic T cell activation takes place in the absence of thymic development.

Ig Heavy Chain Third Complementarity Determining Regions (H CDR3s) After Stem Cell Transplantation Do Not Resemble the Developing Human Fetal H CDR3s in Size Distribution and Ig Gene Utilization

Previous studies have suggested that the B-cell repertoire after stem cell transplantation resembles the developing repertoire in the fetus. Fetal and adult repertoires differ strikingly at the molecular level in Ig heavy chain third complementarity determining region (H CDR3) size distribution and Ig gene utilization. Previously, the posttransplant repertoire has not been studied fully in this regard. In this study, we analyzed H CDR3s posttransplant using CDR3 fingerprinting, single-strand conformation polymorphism (SSCP), and random sequencing. Eleven adult patients who received either autologous (n = 6) or allogeneic adult sibling (n = 5) hematopoietic stem cell transplants were studied. IgM H CDR3 repertoires demonstrated limited clonal diversity within the first 6 to 10 weeks posttransplant. By 3 to 4 months, the IgM H CDR3 repertoires were as diverse as those in healthy adults. Reconstitution of the IgM diversity correlated with the expansion of the multimember VH3 family. By contrast, the contribution of the single-member VH6 family was limited in most patients up to 6 to 9 months. No evidence was seen for greater contribution of VH6 posttransplant. IgG repertoires remained clonally restricted at all times. In all patients, H CDR3 sizes fell within adult limits. Direct nucleotide sequencing of H CDR3s showed adult-type N-nucleotide insertions and Ig gene utilization. These results indicate that the emerging repertoire posttransplant does not resemble the developing fetal repertoire at the molecular level.

© 1998 by The American Society of Hematology.

Ig Heavy Chain Third Complementarity Determining Regions (H CDR3s) After Stem Cell Transplantation Do Not Resemble the Developing Human Fetal H CDR3s in Size Distribution and Ig Gene Utilization

Previous studies have suggested that the B-cell repertoire after stem cell transplantation resembles the developing repertoire in the fetus. Fetal and adult repertoires differ strikingly at the molecular level in Ig heavy chain third complementarity determining region (H CDR3) size distribution and Ig gene utilization. Previously, the posttransplant repertoire has not been studied fully in this regard. In this study, we analyzed H CDR3s posttransplant using CDR3 fingerprinting, single-strand conformation polymorphism (SSCP), and random sequencing. Eleven adult patients who received either autologous (n = 6) or allogeneic adult sibling (n = 5) hematopoietic stem cell transplants were studied. IgM H CDR3 repertoires demonstrated limited clonal diversity within the first 6 to 10 weeks posttransplant. By 3 to 4 months, the IgM H CDR3 repertoires were as diverse as those in healthy adults. Reconstitution of the IgM diversity correlated with the expansion of the multimember VH3 family. By contrast, the contribution of the single-member VH6 family was limited in most patients up to 6 to 9 months. No evidence was seen for greater contribution of VH6 posttransplant. IgG repertoires remained clonally restricted at all times. In all patients, H CDR3 sizes fell within adult limits. Direct nucleotide sequencing of H CDR3s showed adult-type N-nucleotide insertions and Ig gene utilization. These results indicate that the emerging repertoire posttransplant does not resemble the developing fetal repertoire at the molecular level.

© 1998 by The American Society of Hematology.

Cytokine gene expression in skin and lymphoid organs in graft versus host disease

AIM

To determine if human graft versus host disease (GvHD) is associated with any detectable change in cytokine gene expression in the skin and lymphoid organs.

METHODS

Reverse transcriptase and the polymerase chain reaction were used to amplify mRNA for interleukins-1 (IL-1), -2 (IL-2), -4 (IL-4) and -6 (IL-6), IL-2 receptor (IL-2R), tumour necrosis factors alpha (TNF-alpha) and beta (TNF-beta), gamma interferon (IFN gamma) and granulocyte macrophage colony stimulating factor (GM-CSF) in frozen punch biopsy specimens of skin and necropsy samples of skin, lymph node, and spleen.

RESULTS

No cytokine mRNA was detected in the punch biopsy specimens except weak signals for IL-6 and IL-1 and GM-CSF in two normal donors and IL2-R in one patient with GvHD. In samples of skin taken at necropsy, however, significant quantities of mRNA for TNF-alpha, TNF-beta, and IL-4 were detected in patients who had or had had GvHD in contrast to those without the disease whose skin lacked mRNA for these products but contained detectable quantities of IL-1, IL2-R, IL-6 and GM-CSF. There seemed to be a reciprocal relation between TNF-alpha and IL-4. In necropsy samples of lymph node and spleen a pattern of cytokine production similar to that in the skin was observed with a preponderance of TNF-alpha, TNF-beta and IL-4 in patients with GvHD and GM-CSF and IL-6 in those without the disease.

CONCLUSIONS

The local synthesis of these molecules would explain many of the morphological and immunohistological features of GvHD. The failure to detect TNF-alpha, TNF-beta, and IL-4 in skin biopsy specimens exhibiting GvHD is probably due to their small size but further investigations are required.

The pathology of bone marrow transplantation

The pathological complications of bone marrow transplantation are complex and may affect any organ in the body. The causes are often multifactorial and include the effects of chemotherapy, the conditioning regimen, drugs used in the post-transplant period such as immunosuppressants and antibiotics, graft-versus-host disease (GvHD) and the effects of the primary disease itself. Infections are common and result from the immunosuppressive effects of cytotoxic drugs and irradiation, GvHD and marrow failure. Haemorrhage is not infrequent. Graft-versus-host disease remains a significant problem and can be difficult to diagnose. Some of its histological features simulate the effects of chemoradiation and the diagnostic lesions may not be present early in the disease, when treatment is most effective. Evidence has accumulated that inflammatory cytokines have a key role in the pathogenesis of GvHD. It can be prevented by eliminating T-cells from the donor marrow but this procedure adversely affects marrow engraftment, increases the changes of rejection and results in a higher incidence of leukaemic relapse. Immunohistochemical staining for various cytokine-inducible molecules has led to some improvement in early diagnosis.

Immunohistology of the human spleen after bone marrow transplantation for leukemia with special reference to the early post-transplantation period

Immunohistochemical investigations were undertaken on paraffin-embedded tissue from the spleens of seven patients who had died after bone marrow transplantation (BMT) for leukemia. Parallel investigations were undertaken on three surgically resected traumatically ruptured (but otherwise normal) spleens and three spleens removed at autopsy from accident victims. 1) Up to ten weeks after BMT, the splenic lymphoid tissue was extremely atrophic. Lymphoid follicles (LFs) and periarteriolar lymphatic sheaths (PALS) were completely absent. A considerable increase in lymphoid cells in the red pulp and formation of small LFs and PALS occurred only in the longest surviving patient, who had died 50 weeks after BMT. 2) B cells (L26+, 4KB5+, Ki-B3+) were almost completely absent in the early post-transplantation period and thus T cells (UCHL1+) represented the major constituent of the hypoplastic splenic lymphoid tissue. Considerable numbers of T cells were already found two weeks after BMT. T-immune-accessory reticulum cells (S-100 protein+) were found in the PALS of the controls, but were absent in three of the BMT recipients. The findings clearly reflect the marked immunodeficiency in the early post-transplantation period, during which many patients (4/7 in this study) die of opportunistic infections, and are in line with the fact that the earliest signs of reconstitution of the immune system have been found to occur at three months post-transplantation. Since six of our BMT recipients had suffered from graft-versus-host disease our findings probably do not fully correspond to those when the immune system undergoes undisturbed reconstitution.

Lymphocyte populations in autopsy bone marrow sections from recipients of allogeneic marrow and non-transplant sudden death cases

Femoral marrow, obtained at autopsy, was stained using immunohistological techniques, for T (CD2+) cells, B (CD19+) cells, helper/inducer (CD4+) T cells, suppressor/cytotoxic (CD8+) T cells and natural killer (HNK1+) cells. The numbers present in 13 recipients of allogeneic marrow, 14 to 140 days after transplantation, were compared with those in marrows from nine subjects with no haematological or malignant conditions. In marrow sections from non-transplant subjects, approximately 8% nucleated cells were CD2+ with CD4+ and CD8+ cells present in nearly equal numbers; 1-3% were CD19+ and generally less than 1% HNK1+. The percentages of CD19+ and CD4+ cells were significantly reduced after bone marrow transplantation but, if a correction factor for marrow cellularity was introduced, then CD2+ and CD8+ cell values were also low. The findings were compared with the number of cells transplanted, the time after transplantation, presence of graft-versus-host disease or infection and peripheral blood white cell count, but no correlation was found.

B lymphocyte regeneration in marrow and blood after autologous bone marrow transplantation: increased numbers of B cells carrying activation and progression markers

The reconstitution of B cells in the bone marrow and peripheral blood was prospectively studied in 27 patients undergoing autologous bone marrow transplantation (ABMT). No major differences in B cell regeneration patterns were recorded between patients receiving marrows purged of B cells (anti-CD10 + 19; n = 17) and patients receiving unpurged marrows (n = 10). Compared with healthy controls, elevated absolute and relative numbers of B cells were recorded in the blood and marrow at +6 and +12 months in both groups of patients. CD23+ B cells were severely depressed during the first three months post ABMT, indicating immaturity. A twofold increase in B cells carrying the activation marker 4F2 was recorded in the marrow at +1 month. Serum immunoglobulin levels (IgG, IgA, IgM) were within low-normal range throughout the study. The depressed B cell responses reported after allogeneic and autologous BMT could in part be explained by the low expression of the CD23 antigen on B cells after such therapy.

Lymph node morphology after allogeneic bone marrow transplantation for chronic myeloid leukemia: a histological and immunohistological study focusing on the phenotype of the recovering lymphoid cells

A histological and immunohistological analysis of lymph nodes after allogeneic bone marrow transplantation (BMT) was performed to investigate the microarchitecture of the lymphatic tissue and the phenotype of the recovering lymphoid cells. The study included four patients with chronic myeloid leukaemia who had died between 0.5 and 12 months after transplantation. The study yielded the following results: 1. All lymph nodes, irrespective of length of the survival period, exhibited severe atrophy of the lymphoreticular tissue with marked depletion of lymphocytes and dilatation of the sinuses. The number of lymphoid cells increased considerably with time after transplantation. 2. The main constituents of the recovering immune system were mature T lymphocytes (CD4+ and CD8+ cells in nearly equal numbers) and macrophages. The earliest signs of recovery of the immune system could already be detected 0.5 month after BMT. 3. Extreme paucity of B lymphocytes was a prominent finding in all lymph nodes studied. True lymphatic follicles and germinal centres were never detected. 4. Polytypic plasma cells were seen in low or moderate numbers mainly in the lymph node sinuses, while neither marked plasmacytic hyperplasia nor even a monotypic pattern were found. 5. Immune-accessory reticulum cells were detected only in the lymph nodes of the patient who survived 12 months. 6. Natural killer cells occurred only in low numbers irrespective of the duration of survival after BMT. Altogether, the histopathological lymph node findings clearly reflect the marked long-standing depression of the immune responses seen after allogeneic bone marrow transplantation. Since three of the four patients had shown signs of acute or chronic graft-versus-host disease, the histological findings presumably do not fully reflect the normal reconstitution of the immune system, but may have been modified by phenomena related to graft-versus-host disease.

Cellular composition of the spleen after human allogeneic bone marrow transplantation

The cellular composition of the spleen has been assessed in 18 patients who died 15-326 days after receiving allogeneic marrow for leukaemia. The white pulp showed marked lymphocyte depletion with no germinal centres, very few B cells, and rare plasma cells. The marginal zone was unrecognizable but there were moderate numbers of T cells in the periarteriolar lymphatic sheaths (PALS), showing great variation in CD4/CD8 ratio. The percentage of CD4+ cells decreased with time post transplant. CD8+ cells were reduced in patients with graft-versus-host disease (GvHD) who also showed no increase in cells staining for activation markers. No T cells were detected expressing immature phenotypes and no differences were detected between patients who received marrow purged or unpurged of T cells. Macrophage numbers appeared normal. Extramedullary haemopoiesis (EMH) was predominantly in the red pulp greater than 30 days after transplantation but more commonly in the white pulp before then. Pyknotic cells were common in seven cases and appeared to be associated with EMH rather than GvHD. Chimaeric studies demonstrated small numbers of donor cells in the PALS at 26 days and larger numbers at 56 days.

Cutaneous leucocyte composition after human allogeneic bone marrow transplantation: relationship to marrow purging, histology and clinical rash

Immunohistological and morphometric techniques were used to study the skin after marrow transplantation with particular reference to the relationship of marrow purging, the presence of a clinical rash and histological changes to leucocyte numbers and phenotype. Recipients of T-cell-depleted marrow showed significant reductions in CD2+, CD4+ and CD8+ T-lymphocytes in the first 22 d after transplantation but not after this time. T-cell numbers in recipients of unpurged marrow were similar to those of normal donors, indicating a rapid repopulation by cells from the graft. Langerhans cells (CD1+ dendritic cells) and macrophages, on the other hand, were present in similar numbers in both groups of patients within the first 22 d; the former in low and the latter in normal numbers. Biopsies exhibiting graft versus host disease showed increases in CD2+, CD4+ and CD8+ T-lymphocytes with significant lowering of the CD4:CD8 ratio. A proportion expressed markers of activation and HNK1+ cells and macrophages were also increased. Biopsies exhibiting epidermal basal abnormalities only (changes identical to graft versus host disease but without detectable leucocyte infiltration on conventional microscopy) showed a minor increase in macrophages and HNK1+ cells but no other leucocyte alterations to suggest a pathogenetic link with graft versus host disease. Langerhans cells were reduced in these biopsies, however, when taken more than 22 d post-transplant, suggesting that the epidermal changes are associated with Langerhans cell damage or repopulation. We were unable to identify any significant alteration in leucocytes in patients with strong clinical evidence of graft versus host disease but with histologically unremarkable biopsies. Although it is possible that perivascular increases in T-cells and expression of activation markers precede the characteristic histological picture of graft versus host disease the time scale is probably too short to allow diagnostic value.

Expression of restricted immunoglobulin isotypes in plasmacellular hyperplasia after allogeneic bone marrow transplantation

Plasmacellular hyperplasia in lymphoid tissue was found in 4 out of 9 patients 1-6 months after allogeneic bone marrow transplantation as treatment for leukaemia. In the plasma cell populations, 13-85% expressed a single immunoglobulin light and heavy chain isotype (monotypic Ig expression). DNA analysis, using a DNA probe specific for heavy chain JH gene segments and for light chains, did not reveal the presence of clonally restricted B lymphocytes. The patients' sera lacked homogeneous immunoglobulins. We conclude that plasmacellular hyperplasia found after allogeneic bone marrow transplantation represents a polyclonal B-cell expansion- with a restriction in Ig isotype.