The distribution of cells expressing a natural killer cell marker (HNK-1) in normal human lymphoid organs and malignant lymphomas

T cells that promote B-Cell maturation in systemic autoimmunity

Follicular helper T (Tfh) cells play an essential role in helping B cells generate antibodies upon pathogen encounters. Such T-cell help classically occurs in germinal centers (GCs) located in B-cell follicles of secondary lymphoid organs, a site of immunoglobulin affinity maturation and isotype switching. B-cell maturation also occurs extrafollicularly, in the red pulp of the spleen and medullary cords in lymph nodes, with plasma cell formation and antibody production. Development of extrafollicular foci (EF) in T-cell-dependent (TD) immune responses is reliant upon CD4(+) T cells with characteristics of Tfh cells. Pathogenic autoantibodies, arising from self-reactive B cells having undergone somatic hypermutation with affinity selection and class switching within GCs and EF, are major contributors to the end-organ injury in systemic autoimmunity. B cells maturing to produce autoantibodies in systemic autoimmune diseases, like those in normal immune responses, largely require T-helper cells. This review highlights Tfh cell development as an introduction to a more in-depth discussion of human Tfh cells and blood borne cells with similar features and the role of these cells in promotion of systemic autoimmunity.

IgG4-Related Disorder of the Retroperitoneum Resembling Castleman’s Disease Plasma Cell Type: A Report of 2 Cases

This study reports 2 cases of IgG4-related disorder of the retroperitoneum resembling plasma cell type of Castleman’s disease. A single lesion was located in the renal hilum and ureter, respectively, in these 2 cases. Histologically, both lesions were characterized by reactive follicular hyperplasia with active germinal centers and a sheet of polyclonal mature plasma cells in the interfollicular area. The prominent sclerosis and/or fibrosis, which were characteristic histological findings of IgG4-related disorders, were absent. However, immunohistochemical study demonstrated numerous IgG4+ plasma cells accounting for more than 50% of IgG+ cells. The phlebitis that occurs with early lesions of obliterative phlebitis is one of the characteristic histological findings of IgG4-related disorders and was noted in one case. Serum IgG4 concentration was increased in one case. The serum interleukin-6 level was within the normal range in one case that was examined. From a therapeutic perspective, it is important to discriminate IgG4-related disorder from plasma cell type of Castleman’s disease.

"Follicular variant" of hyaline-vascular type of Castleman's disease: histopathological and immunohistochemical study of 11 cases

Occasionally, the hyaline-vascular type of Castleman's disease (HVCD) contains numerous lymphoid follicles which usually occupy more than 50% of the lesion. Such lesions are called the follicular variant (FV) of HVCD. To clarify the histological and immunohistochemical findings of lymphoid follicles in the FV of HVCD, we examined 11 such cases. Histologically, five types of lymphoid follicles were delineated. Lymphoid follicles ; (i) with normal germinal centers (GCs) ; (ii) showing follicular lysis ; (iii) with progressive transformation of GC (PTGC) ; (iv) where the large nodule of mantle zone lymphocytes contained multiple small atrophic GCs (multiple GC pattern) ; and (v) where the large, often irregularly shaped nodules of mantle cells radically penetrated small vessels with inconspicuous GCs. These nodules somewhat resembled primary lymphoid follicles (primary follicular pattern). The majority of lymphoid follicles in all 11 cases were of the primary follicular pattern and/or multiple GC pattern. However, three lesions also contained normal germinal GC, while two contained normal GC, follicular lysis and PTGC and one other contained normal GC and PTGC. Moreover, in 3 cases of primary follicular pattern, the majority of the lymphoid follicles were surrounded by a pale cuff of mantle cells. Because of the presence of numerous lymphoid follicles, the FV of HVCD should be sometimes differentiated from Hodgkin lymphoma and low-grade B-cell lymphomas showing follicular growth pattern. Recognition of the histological and immunohistochemical findings of the FV of HVCD is needed to avoid overdiagnosis.

Immunomodulation of early engrafted natural killer cells with interleukin-2 and interferon-alpha in autologous stem cell transplantation

High relapse rates during the first year after autologous stem cell transplantation (ASCT) for multiple myeloma or non-Hodgkin lymphoma are due to the failure of high-dose chemotherapy to eradicate minimal residual disease. Post-ASCT immunorecovery studies have shown that quantities of natural killer (NK) cells return to normal within 1 month post-ASCT in contrast to the recovery of T and B cell populations (up to 1 year). Preclinical studies have demonstrated that NK cells have potent antitumor activity. IL-2 and IFN-alpha enhance NK-cell activity. We investigated the efficacy of IL-2 and IFN-alpha to up-regulate NK-cell cytotoxicity at 14 days post ASCT. Twenty patients undergoing ASCT had PBMCs collected pretransplantation and at 14 days post transplantation. PBMCs (effector cells) from each blood sample were incubated in vitro with IFN-alpha and IL-2 at 10000 IU/ml. NK cell activity was determined by sodium chromate (51)Cr release assay for lysis of K562 target cells. IL-2 and IFN-alpha each increased lysis of K562 cells compared with placebo (effector-to-target ratio, 50:1, P < 0.001). Increased NK cell activity occurred in samples from all patients. IL-2 and IFN-alpha up-regulated NK cell activity at 14 days post ASCT. They may be useful as immunomodulators as early as 14 days post ASCT to eradicate or control minimal residual disease.

Expression of T-cell receptor (TCR)alpha chain on normal human tonsils and T-cell lymphomas

We analyzed immunohistologically the expression of T-cell receptor (TCR)alpha chain on human tonsils and on T-cell lymphoma (T-ML) tissues using the avidin-biotin-peroxidase method. A murine monoclonal antibody alpha F1, specific for the constant region of the TCR alpha chain, was employed. On normal tonsil, alpha F1-positive cells were observed mainly in T-zones and germinal centers. In T-zones, the staining intensities varied markedly, with heavy staining evident in less than one fourth. In germinal centers, a proportion of stained cells showed a histiocytic pattern with small cytoplasmic projections. All the T-ML tissues expressed TCR alpha, whereas the staining intensities varied among cases and among lymphoma cells. No correlations were observed in the expressions of TCR alpha chain and other T-cell markers including CD3, CD4 and CD8.

Reactive proliferative lesions in lymph nodes from rheumatoid arthritis patients. A clinicopathological and immunohistological study

In 22 cases of rheumatoid arthritis (RA), including 4 cases of malignant RA (MRA), reactive proliferative lymph node lesions were studied clinicopathologically and immunohistochemically. This series included 5 males and 17 females. The period between disease onset and lymph node biopsy ranged from 3 months to 41 years. Generalized lymphadenopathy was noted in 13 cases and constitutional symptoms in 8. The histological findings characteristic of RA were 1) follicular hyperplasia with active germinal centers and 2) polyclonal plasma cell infiltration in the interfollicular area. Studies of intracytoplasmic immunoglobulin showed that gamma-heavy chain-expressing plasma cells were a major component in the interfollicular area in 17 RA cases. However, in 4 MRA cases, a prominent increase of mu chain-expressing plasma cells was recognized in the same area. In the 3 cases for which fresh tissue sections were stained with monoclonal antibodies against lymphocytes, we found that the majority of T cells in the interfollicular area had helper/inducer markers. The identical locations of the T cell population and plasma cells indicated that both played a role in the proliferation and/or differentiation of B cells in lymph nodes in RA.

Deterioration of B cell proliferation correlates with dendritic reticulum cell destruction in germinal centers of an AIDS patient. Case study

A lymph node from a bisexual Caucasian male infected with human immunodeficiency virus (HIV) and in the persistent generalized lymphadenopathy (PGL) stage was studied. Dendritic reticulum cells (DRCs) were well preserved in over half of the germinal centers (GCs), while in the rest, they showed marked destruction, producing patchy or rather wide DRC-depleted areas. Proliferation-associated antigens, i.e., PC antigen and DNA-polymerase alpha, were demonstrated in nuclei of germinal center B cells in areas where the DRC network was intact, while they were prominently depleted in areas where the DRC network was lost. The p-24 viral core antigen was shown to be localized in DRCs, especially those in the process of degeneration. These results suggest that the DRC in this patient, when infected with HIV, were destroyed, and that the resulting DRC depletion led to the suppression of B cell proliferation in GCs.

A light microscopical study of isolated follicular dendritic cell-clusters in human tonsils

In order to re-examine the cellular structure of isolated FDC-culsters in the germinal centers of human tonsils, a light microscopical analysis was made. Approximately 14 FDC-clusters were recovered from one enucleated germinal center using the enzyme digestion technique. The minimum unit of the FDC-clusters was composed of one FDC and 8 to 9 lymphocytes. Most of the FDC-clusters were representative of the microenvironment of the light zone at the germinal center in situ. Half of the engulfed centrocytes were supposed to be at the Go phase, and the others at the G1 to G2 phase. It is suspected that the helper-T cell has some relationship to the FDC microenvironment, and that the suppressor-T cell does not. Most of the CIgG-containing cells in the germinal centers were considered to have infiltrated into the interspace of the FDC microenvironment.

Expression of the HNK-1 carbohydrate epitope in human retina and retinoblastoma. An immunohistochemical study with the anti-Leu-7 monoclonal antibody

Fifty formalin-fixed and paraffin-embedded retinoblastoma specimens and five normal human eyes were studied with the monoclonal anti-Leu-7 antibody, directed against the HNK-1 carbohydrate epitope that is shared by human natural killer cells and many neuronal, glial and neuroectodermal cells. The laboratory method was a sensitive immunohistochemical staining procedure, and neuroectodermal tumours that usually express this epitope were used as positive controls. In the human retina, Müller cell membranes were positively stained, but additional staining of neuronal cells was not excluded at the light microscopical level. A positive cytoplasmic reaction was also seen in ciliary and retinal pigment epithelial cells. All but one intraocular retinoblastomata studied contained cells staining positively for the HNK-1 epitope, but these cells were probably not neoplastic. Although positive reaction has previously been reported in three retinoblastomata, the present results suggest that positive cells are derived from entrapped and infiltrated retina. Staining of adjacent sections against leukocyte common antigen suggested that the positively staining cells were not natural killer cells.

Definite spontaneous cell-mediated cytotoxicity and HNK-1 cells in the human large intestine

Spontaneous cell-mediated cytotoxicity (SCMC) and the marker of natural killer (NK) cells mediating SCMC of the human large intestine were studied. Lamina proprial lymphoid cells (LPL) were isolated by sequential dithiothreitol-EDTA-collagenase treatment of the gut specimen. SCMC was measured by the chromium release method. Target cells included P4788 in monolayer, a cell line derived from colon cancer, Chang cells in monolayer, and K562 in suspension. Target cells in monolayer including colon cancer cell line were chosen because they were thought to be more appropriate to assess SCMC for lymphoid cells in the solid organ. While lower compared to cytotoxicities (CT) by peripheral blood lymphoid cells (PBL), define CT were observed in LPL against all three targets. NK cells marker was studied both on LPL by an indirect fluorescent antibody method and on the gut tissue by indirect immunoperoxidase staining using anti HNK-1 monoclonal antibody which defines virtually all NK cells. HNK-1 positive (HNK-1 +) cells were identified in both methods. HNK-1 + cells were observed in the epithelium, lamina propria, and lymph follicle with or without germinal centers. These results clearly demonstrated the presence of SCMC and HNK-1 + cells in the human large bowel.

Infiltration density of HNK 1 positive cells in non-Hodgkin's lymphomas depends on histologic subtype: an in situ morphometric analysis

Numbers and distribution of HNK-1 (Leu 7) positive cells within 115 malignant Non-Hodgkin's lymphomas (NHL) were evaluated in situ by immunomorphometry. Results on the infiltration were related to histological and clinical parameters. A mean of 4.099 +/- 350 HNK 1+ cells/microliter tumor tissue was found, which was comparable to normal (reactive) lymphatic tissues (4.441 +/- 1.235) and was about a quarter of the population density of T helper/inducer (TH) and T cytotoxic/suppressor (TS) lymphocytes together. The distribution of HNK 1+ cells within the tumors was diffuse except in nodular lymphomas of follicular center cell origin (centroblastic/centrocytic = cb/cc NHL). When evaluating the different histological subgroups, the highest number of HNK 1+ cells was found within the tumor areas of cb/cc, which contained about three times as many positive cells as the other NHL. High numbers were also found in the diffuse variant of cb/cc but not in centrocytic NHL. Different degrees of HNK 1+ cell densities were observed in lymphocytic lymphomas (4.426 +/- 754), with high numbers in about 30% of the patients. Splenic tissues of 6 hairy cell leukemias displayed lower numbers of HNK 1+ cells as compared with other low grade malignant NHL. In "large cell" NHL, the lymphoblastic subtype showed only sparse HNK 1+ cells (1.345 +/- 386). The number was significantly reduced in comparison to all other NHL (p less than 0.01) and markedly lower than in the other NHL of high malignancy (immunoblastic and centroblastic NHL, p less than 0.02). The diminuation was not due to a simple dilution phenomenon in a rapidly proliferating tumor, as TH and TS infiltrates were comparable to other NHL. Correlating results with the clinical course (available in 58 patients), significantly higher numbers of HNK 1+ cells were found in NHL of low malignancy (p less than 0.02), but patients with a favourable course did not differ from those with progressive disease (p less than 0.5). Patients treated by cytotoxic drugs showed higher numbers of HNK 1+ cells than those before or without treatment (p less than 0.02). Results on TH and TS cell numbers in comparison to HNK 1+ cells showed completely different patterns of infiltration.

Immunohistochemical studies on human brain tumors using anti-Leu 7 monoclonal antibody in paraffin-embedded specimens

Using the four-step peroxidase-antiperoxidase (PAP) method, the presence of the antigen recognized with anti-Leu 7 monoclonal antibody was investigated in paraffin-embedded human brain tissue and tumors. The antigen was demonstrated in the myelin sheaths, oligodendrocytes, and some choroid plexus cells in normal brain and in oligodendrogliomas, some astrocytomas and choroid plexus papillomas. The technique can be used to identify normal and neoplastic oligodendrocytes.

Distribution of Leu 7 (HNK-1) antigen in human digestive organs: an immunohistochemical study with monoclonal antibody

Leu 7 immunoreactivity was demonstrated with the indirect peroxidase-labelled antibody method on frozen and paraffin-embedded tissue sections of human digestive organs. Anti-Leu 7 monoclonal antibody, which allegedly detects mononuclear cells with natural killer or killer activity, recognized lymphoid cells among intestinal epithelial cells and in the germinal centres of solitary lymphoid follicles of small and large intestine, and a few in gallbladder, liver and the lamina propria of the intestine. In addition, peripheral nerve fibres, endocrine cells in the gut and pancreas and carcinoid and islet cell tumours were also positively stained. At the ultrastructural level, Leu 7 antigen was localized on the plasma membrane of granulated lymphoid cells in the gut mucosa and on the secretory granules of intestinal endocrine cells. In normal pancreas, Leu 7 immunoreactivity was demonstrated in most cells containing pancreatic polypeptide and in many cells containing somatostatin or glicentin. Insulin-containing cells, however, lacked Leu 7 immunoreactant. These findings were obtained in both frozen sections and paraffin-embedded sections. The possible cross-reactivities of monoclonal antibodies are discussed as they raise an important caveat in immunohistochemical studies using these antibodies.

Functional anatomy of germinal centers

This year we celebrate the first centennial of the discovery of germinal centers by Flemming in 1884. The present paper reviews and adds new data to the functional anatomy of a germinal center. Emphasizing its reactive nature, we first describe a germinal center reaction and then deal with its infrastructural aspects and constituent cell populations, both lymphoid and nonlymphoid. Elements involved in the de novo formation of a germinal center, like antigen, T cells, and the mysterious germinal-center-precursor cell, are discussed. Next, attention is paid to the requirements for lymphoid cells to migrate into germinal centers, and novel features of germinal-center-seeking cells are presented. Subsequently, we discuss kinetic aspects of the high proliferative activity in a germinal center; and finally a description of the functional capacities of germinal-center-derived cells, such as B memory cells and IgM-antibody-forming cell precursors, completes this picture of present-day knowledge of the germinal center, a structure which has yet to reveal its last secrets.

Characterization of human granular lymphocyte subpopulations expressing HNK-1 (Leu-7) and Leu-11 antigens in the blood and lymphoid tissues from fetuses, neonates and adults

Three subpopulations of human granular lymphocytes from blood and lymphoid tissues were characterized using combinations of the monoclonal antibodies (mAb) HNK-1 (Leu-7), Leu-11 and VEP13. Each subpopulation was confirmed to possess natural killer (NK) cell functional capability, but a different level of cytotoxic efficiency (HNK-1+leu-11- less than HNK-1+Leu-11+ less than HNK-1-Leu-11+). In adult from 23 healthy donors, the subpopulations with HNK-1+Leu-11-, HNK-1+Leu-11+ and HNK-1-Leu-11+ phenotypes comprised 4.7 +/- 3.0, 8.0 +/- 6.4 and 3.9 +/- 3.5% of mononuclear cells, respectively. Despite their distinct surface marker phenotypes and NK functional ability, all 3 subpopulations exhibited granular lymphocyte morphology. One of these subpopulations, HNK-1+Leu-11-, also expressed the pan-T cell antigen Leu-4. Different patterns were observed in fetal bone marrow and cord blood, where the vast majority of HNK-1+ cells lacked the Leu-11 antigen (HNK-1+Leu-11+ cells). The HNK-1 antigen was not expressed on granulocytes and their precursors, whereas both Leu-11 and VEP13 antigens were expressed on these myeloid cells from fetal bone marrow and cord blood as well as adult bone marrow and spleen. Cell lines of granular lymphocytes cultured in the presence of interleukin 2 all possessed the HNK-1+Leu-4+ phenotype and NK functional capability but lacked the Leu-11 and VEP13 antigens on their surface after 15 days of culture. Although granular lymphocytes expressing the Fc receptors reacting with the mAb Leu-11 and VEP13, are the most functionally active NK cells, the HNK-1+ subpopulation lacking the Leu-11 and VEP13 antigens appears to be an important population (possibly an immature form of granular lymphocytes) for delineating the cell lineage(s) and differentiation of human granular lymphocytes. Although none of the currently available mAb react both inclusively and exclusively with human granular lymphocytes, the combination usage of these antibodies permits a more precise and comprehensive analysis of these subsets.

Lymphocyte subsets in the white pulp of human spleen in normal and diseased cases

The distribution of T and B lymphocytes and their subsets in the white pulp of human spleens extirpated from patients with cancer of the digestive tract and those with portal hypertension was examined with the appliance of monoclonal antibodies. T lymphocytes were distributed in the core of lymphatic sheath protuberance (Matsumoto), while the mantle zone of lymphatic nodule and germinal center were solely occupied by B lymphocytes. On the other hand, both T and B lymphocytes were found in the cortical zone of lymphatic sheath protuberance and outer and inner layer of lymphatic nodule. The ratio of both cells differed from one case to the other. The majority of T lymphocytes in the core of lymphatic sheath protuberance and those localized in the light region of germinal center were helper T cells. Although the lymphatic sheaths in cases with portal hypertension were narrower than those in the controls, there was no difference in the distribution density of T cells between the two groups. Hardly any B lymphocytes were found in the cortical zone of lymphatic sheath protuberance, while the mixture of T lymphocytes tended to become prominent in the outer and inner layer of lymphatic nodule in those cases.