Leu-7-positive cells with monocyte phenotype show different ultrastructural features in comparison to Leu-7-positive cells with T-cell phenotype

The ultrastructural features of the Leu-7-positive - Leu-M3-positive cell subpopulation and the Leu-7-positive - Leu-4-positive cell subpopulation were characterized and compared using immunogold-immunoperoxidase double labelling with immunoelectron microscopy. The majority of Leu-7-positive cells coexpressed a monocyte phenotype and showed an ultrastructural pattern specific for functional natural killer (NK) cells, i.e. a low nuclear/cytoplasmic (N/C) ratio, an irregular outline, many cytoplasmic organelles and electron-dense granules. In contrast, only a minority of Leu-7-positive cells coexpressed a T phenotype, and these were characterized by a high N/C ratio, an even surface and the absence of electron-dense granules. Thus, Leu-7-positive - Leu-4-positive cells may by an immature form of NK cells, and Leu-7-positive - Leu-4-positive and Leu-7-positive - Leu-M3-positive cell subpopulations may represent different stages of Leu-7-positive cell differentiation.     

Ultrastructural characterization of human large granular lymphocyte subsets defined by the expression of HNK-1 (Leu-7), Leu-11, or both HNK-1 and Leu-11 antigens

A peroxidase-colloidal gold double labeling system in immunoelectron microscopy was used to investigate the ultrastructural features of human large granular lymphocytes (LGL) subpopulations. Three subsets of LGL, Leu-7+-Leu-11-, Leu-7+-Leu-11+, Leu-7- -Leu-11+, were characterized using combinations of the monoclonal antibodies anti-Leu-7 and anti-Leu-11. They showed different ultrastructural patterns. In fact, Leu-7+-Leu-11- cells showed a high nuclear/cytoplasmic ratio (N/C), a round nucleus, a cytoplasm with few organelles, and a rather even surface. Moreover, most of them lacked electron-dense granules. On the other hand, Leu-11+ cells displayed a low N/C, an irregular-shaped nucleus, and a cytoplasm containing a well-developed Golgi apparatus, many mitochondria, vacuoles, vesicles, and numerous electron-dense granules. Moreover, they exhibited an irregular cell surface. Thus, Leu-7+-Leu-11- cells seemed to represent an immature form of LGL, while cells expressing the Leu-11 antigen showed a fine structure specific for functional NK cells. Our findings suggest that the expression of HNK-1 (Leu-7) and Leu-11 antigens respectively represents subsequent stages in NK cell differentiation.     

A large subpopulation of lymphocytes with T helper phenotype (Leu-3/T4+) exhibits the property of binding to NK cell targets and granular lymphocyte morphology

A discrete subpopulation of lymphocytes sharing several phenotypic characteristics with natural killer (NK) cells was identified within the circulating pool of human lymphocytes that bear the T helper marker Leu-3. This Leu-3+ subpopulation of cells formed cell conjugates with the NK target cell lines K562 and MOLT-4, but did not bind to mouse myeloma and hybridoma cell lines that are insensitive to NK cells. The Leu-3+ lymphocytes binding to NK cell targets contained cytoplasmic granules similar in ultrastructure and cytochemistry to those previously defined in granular lymphocytes with NK function, except that the granules in Leu-3+ cells were smaller and fewer in number. Unlike classical NK cells, however, the granular Leu-3+ cells did not kill the target cells to which they bound, even after treatment with interferon. The proportion of granular Leu-3+ cells with the capacity to bind to NK cell targets was approximately 7% at birth and increased to approximately 21% of the Leu-3+ cells in adults. These observations suggest the possibility of a lineal relationship between the granular Leu-3+ cells and granular Leu-3- cells with NK capability.     

Morphometric characterization of NK cell subset expressing the Leu-11 antigen in comparison to Leu-7 positive, 11 negative cells

Three subpopulations of human natural killer (NK) cells were identified by immunoelectron microscopy, using combinations of anti-Leu-7 and anti-Leu-11 monoclonal antibodies. For each subpopulation the nuclear area/cellular area ratio (An/Ac) and the perimeter/equivalent circumference ratio were evaluated employing an interactive image analyzer. Leu-11+ cells showed a larger area, a smaller An/Ac and a higher "villousity degree" in comparison to Leu-7+, 11- cells. These differences were proved to be significant using the Kolmogorov-Smirnov two sample test. Previous studies described the existence of distinct cytotoxic capability, recombinant interleukin 2-mediated activation, and ultrastructural features of Leu-11+ in comparison to Leu-7+, 11- cells. This is the first report in which morphometric differences within NK cell subsets are exactly determined.     

Anti-lymphocyte antibody Leu-7 (HNK-1) recognizes a constituent of neuroendocrine granule matrix

Anti-lymphocyte monoclonal antibody HNK-1 (Leu-7) reacts with the cell surfaces of natural killer (NK) lymphocytes and with myelin-associated glycoprotein (MAG). This antibody reacts intensely with normal and neoplastic adrenal medullary cells. A small proportion of normal pancreatic islet cells, anterior pituitary, and gastroenteropancreatic endocrine cells also show Leu-7 immunoreactivity. In adrenal medulla, ultrastructural immunocytochemical studies and immunoblot analyses reveal that Leu-7 reacts with an intracellular protein of MW 75 KD which is localized within the matrices of the chromaffin granules. The MW of this protein differs from those of MAG and chromogranin A. The findings suggest that Leu-7 immunoreactivity might be a new marker for specific subsets of secretory granules.     

Leu-11+ lymphocytes with natural killer (NK) activity are precursors of recombinant interleukin 2 (rIL 2)-induced activated killer (AK) cells

Precursors of activated killer (AK) cells cytotoxic for human noncultured metastatic melanoma and colon carcinoma were characterized. These cells required 3 days incubation with recombinant interleukin 2 (rIL 2) and DNA synthesis for the induction of AK activity. Both negative and positive cell purification methods were used to identify the subpopulation of cells containing AK precursors. By complement-mediated cell depletion studies, AK precursors were largely present in the Leu-11+ fraction, and to a much lesser extent in the Leu-7+ and Leu-2a+ fractions; they were absent in Leu-3a+ and Leu-4+ cells. Lymphocyte subpopulations were then purified with a cell sorter to positively select for the subset containing AK precursors. Leu-11+ cells had the highest level of AK activity and proliferative response when cultured for 3 days with rIL 2 as well as the highest level of NK activity before culture. Leu-7+ cells had neither AK activity nor a proliferative response when cultured with rIL 2, although they still possessed high NK activity. The same levels of AK and NK activity were found in Leu-2a+ and Leu-2a- fractions, but both activities were absent among Leu-4+ and Leu-3a+ cells. Further fractionation with a two-step sorting technique showed that the highest AK activity resided in the Leu-7-Leu-11+ cell fraction. Morphologically, this subfraction was granular lymphocytes. Titration experiments or rIL 2-responsive cells showed that the number of cells required to achieve a comparable level of rIL 2 proliferative response were as follows: 35 X 10(3) cells from unseparated PBL, 10 X 10(3) cells from Leu-11+ cells, 3.3 X 10(3) from Leu-7-Leu-11+ cells, and 640 X 10(3) cells from Leu-7+ cells. These results indicate that the lymphocyte subpopulation that proliferates in the presence of rIL 2 and then develops AK activity was a subpopulation of Leu-11+ granular lymphocytes, which also possessed the highest NK activity. These Leu-11+ cells lacked the antigens defined by the Leu-7, Leu-3a, or Leu-4 antibodies. Although Leu-7+ cells did not respond to rIL 2 by themselves, they may play a role in the induction of AK activity.     

Role of CD2 in activation and cytotoxic function of CD8/Leu-7-positive T cells

CD3/CD8-positive, Leu-7-positive cells comprise about 3 to 5% of PBL in normal individuals, but the proportion of these cells is increased in patients with a variety of diseases including chronic viral infection, Crohn's disease, and AIDS. To study further the function of these cells, the proliferative and cytotoxic responses of highly purified CD8/Leu-7-positive cells were studied in vitro. These cells had low proliferative responses when exposed to PHA or mitogenic anti-CD3 mAb compared to CD8/Leu-7-negative cells, and their proliferative responses were significantly lower after addition of IL-2 or autologous adherent cells. However, the proliferative responses of both Leu-7-positive and Leu-7-negative CD8 cells were similar when stimulated with PHA, Ionomycin, or anti-CD3 in combination with phorbol ester. In addition, CD8/Leu-7-positive cells demonstrated high proliferative responses when exposed to a combination of both PHA and SRBC, and these responses could be inhibited by prior addition of non-stimulating anti-CD2.1 mAb. CD8/Leu-7-positive cells, but not CD8/Leu-7-negative cells, mediated lectin- and anti-CD3-induced cytotoxicity against K562 target cells. Cytotoxicity was in part dependent on the CD2 Ag because it was inhibited by anti-CD2.1 mAb. Finally, when small CD8-positive T cells having low cytotoxic potential were activated with PHA plus SRBC, but not PHA alone, there was significant enhancement of their cytotoxic function. Thus, the CD2 receptor may be an important activation pathway for cytotoxic cells.     

Two-color immunofluorescence and flow cytometry analysis of lymphocytes in long-term renal allotransplant recipients: identification of a major Leu-7+/Leu-3+ subpopulation

Using two-color immunofluorescence with fluorescein isothiocyanate (FITC)- and phycoerythrin (PE)-labeled monoclonal antibodies to human lymphocyte antigens and flow cytometry, we studied lymphocyte subsets in 16 long-term renal allotransplant recipients at risk for a mean of 78 +/- 15 mo. The absolute number of Leu-1+, Leu-2a+, and Leu-3a+ lymphocytes is significantly decreased compared with a control population, whereas Leu-7+ and Leu-15+ subsets remain unchanged despite standard chronic immunosuppression (azathioprine and prednisone). Within the Leu-7+ subset, we found various phenotypes. Doubly fluorescent lymphocytes Leu-7+/Leu-1+ and Leu-7+/Leu-2a+ are not significantly different in the transplant population compared with a normal control population. The Leu-7+/Leu-3a+ subpopulation is seen to be significantly elevated, and the Leu-7+/Leu-15+ subpopulation decreases significantly. The relationship between the modification of these two phenotypes within the Leu-7 subset may be an important correlate of decreased NK cell activity in long-term renal allotransplant recipients. These Leu-7+/Leu-3a+ cells, normally less than 1% of peripheral blood lymphocytes, have no known functional activity.     

Immunohistologic and immunoelectron microscopic characterization of the mucosal lymphocytes of human small intestine by the use of monoclonal antibodies

Monoclonal antibodies reactive with T cells, T cell subsets, B cells, monocytes, and natural killer cells were used to characterize the nature of mucosal lymphocytes in the human small intestine by application of the immunoperoxidase technique to tissue sections for light and electron microscopic examination. In addition, for comparison, peripheral blood mononuclear cells (PBL) were studied by immunoelectron microscopy. Most of the intraepithelial lymphocytes (IEL) were T cells (Leu-1+, T3+) and expressed the phenotype associated with cytotoxic/suppressor T cells (Leu-2a+, T8+). In contrast, a majority of T lymphocytes in the lamina propria expressed the phenotype associated with helper/inducer T cells (Leu-3a+, T4+). These observations confirm and extend the findings previously reported. In addition, a small number of cells in the lamina propria with the ultrastructural features of macrophages were found to react with anti-Leu-3a and anti-T4 antibodies. Although many IEL contained cytoplasmic granules and had ultrastructural features similar to those of circulating granular lymphocytes, none of these cells reacted with anti-Leu-7 (HNK-1), anti-T10, or anti-M1 antibodies. This suggests that IEL may not be related to circulating large granular lymphocytes, which are Leu-7+, T10+, M1+ and are associated with natural killer activity. Not only Leu-7+ PBL, but T8+, T4+, or T3+ mucosal lymphocytes or PBL also may contain cytoplasmic granules. Therefore, the cytoplasmic granules are not restricted to one cell type, in particular, to Leu-7+ cells.     

Morphologic and phenotypic features of the subpopulation of Leu-2+ cells that suppresses B cell differentiation

The Leu-2 antigen is expressed on a subpopulation of human T cells that perform suppressor and cytotoxic functions. In addition, this antigen is also present on a portion of cells with morphologic characteristics of granular lymphocytes. Although both Leu-2+ cells and granular lymphocytes have been shown to suppress B cell differentiation, the interrelationship of these two suppressor populations has not previously been fully characterized. We recently produced a monoclonal antibody, termed D12 (anti-Leu-15), which reacts with a variety of cell types, including a subpopulation of Leu-2+ cells. Previous studies have indicated that the Leu-2+ cells that suppress T cell proliferative responses express the Leu-2+15+ phenotype, whereas the precursor and effector cytotoxic T cells that recognize class I major histocompatibility antigens are Leu-2+15- lymphocytes. For this report, we used the anti-Leu-2 and anti-Leu-15 monoclonal antibodies and fluorescence-activated cell sorter techniques to characterize the E+ cells that suppress PWM-induced B cell differentiation. These studies indicate that the vast majority of Leu-2+ cells that suppress this T cell-dependent B cell response have the Leu-2+15+ phenotype. Furthermore, when the morphologic and cytochemical characteristics of these Leu-2+15+ cells were studied, virtually all of these cells were granular lymphocytes. Most of the Leu-2+15+ suppressor cells co-expressed the HNK-1 (Leu-7) antigen, which is detected only on granular lymphocytes. In contrast, virtually none of the Leu-2+15+ granular lymphocytes expressed Fc receptors for IgG molecules. These data indicate that the Leu-2+ cells that suppress PWM-induced B cell differentiation are Leu-2+15+ (and predominantly Leu-7+) granular lymphocytes that do not express Fc receptors. The implications of these observations concerning the relationship of human Leu-2+ suppressor cells to murine Ly-2+ cells and the lineage of granular lymphocytes are discussed.     

Production of B cell growth factor by a Leu-7+, OKM1+ non-T cell with the features of large granular lymphocytes (LGL)

The present study reports the characterization of a non-T cell from human peripheral blood which is capable of releasing BCGF. This BCGF-producing non-T cell had a T3-, T8-, Leu-7+, OKM1+, HLA-DR-, Leu-11- surface phenotype and was likely to belong to the so-called large granular lymphocyte (LGL) subset because: after fractionation of non-T cells according to the expression of Leu-7 or HLA-DR markers, it was found in the Leu-7+, HLA-DR- fractions that were particularly enriched in LGL; it co-purified with LGL on Percoll density gradients; and it expressed Leu-7 and OKM1 markers that are shared by a large fraction of LGL. Although co-purified with cells with potent NK capacities, the BCGF-producing cell was not cytotoxic, because treatment of Leu-7+ cells with Leu-11 monoclonal antibody and complement abolished the NK activity but left the BCGF activity unaltered. The factor released by this LGL subset was not IL 1 or IL 2 mistakenly interpreted as BCGF, because: a) cell supernatants particularly rich in BCGF activity contained very little or no IL 1 or IL 2; b) BCGF-induced B cell proliferation was not inhibitable by anti-Tac antibodies (this in spite of the expression of IL 2 receptor by a proportion of activated B cells); and c) BCGF activity was absorbed by B but not T blasts.     

Interferon-alpha induction of lymphocytes containing parallel tubular structures

The induction by IFN-alpha in peripheral blood lymphocytes of parallel tubular structures (PTS) and/or electron-dense granules occurring in a minority of peripheral blood lymphocytes was examined. IFN reportedly augments natural killer (NK) cell activity of large granular lymphocytes (LGL); these cells contain PTS and/or electron-dense granules. Normal peripheral blood mononuclear cells were incubated with IFN-alpha and surface antigen expression was measured by means of indirect immunofluorescence and, at the ultrastructural level, using gold labelled monoclonal antibodies. Surface antigen reactivity with the monoclonal antibodies OKT 3, 4, 8 and Anti-Leu-7 (HNK-1) showed no difference between the IFN-alpha incubation and non-IFN-alpha groups. However, electron microscope investigation revealed significant absolute increases in the percentage of OKT 8+ and Anti-Leu-7+ cells which were PTS-positive after IFN-alpha treatment compared with the control groups. The cytotoxicity assay using the K562 cell line showed enhanced lytic activity. Our results suggest that cells coexpressing the OKT 8 and Leu-7 antigens may be responsible for a minor proportion of the increase in PTS but that IFN-alpha mainly induces PTS and/or associated structures in cells which express the OKT 8+ antigen. These PTS+/OKT 8+ cells may contribute to enhanced cell cytotoxicity.     

Decreased population of Leu-7+ natural killer cells in lymph nodes of homosexual men with AIDS-related persistent lymphadenopathy.

Natural killer (NK) cells were studied in the lymph nodes of homosexual men with the persistent lymphadenopathy syndrome (PLS) and other signs of the disease complex related to the acquired immune deficiency syndrome (AIDS). The NK cells were identified by their Leu-7+ phenotype and enumerated in frozen sections of lymph nodes in conjunction with the quantification of T-lymphocyte subsets. Lymph nodes from patients with AIDS-related PLS contained 91% and 81% fewer NK cells than normal lymph nodes and lymph nodes from patients with non-AIDS-related hyperplastic lymphadenopathy respectively. This decrease in NK cells in PLS is consistent with the immune dysregulation leading to persistent infection and neoplasia in AIDS.     

Multiple myeloma: an immunologic profile. IV. The EA rosette-forming cell is a Leu-1 positive immunoregulatory B cell

Patients with myeloma have a depressed capacity to respond to antigenic challenge. Studies in this laboratory have previously described an unclassified lymphoid cell which binds human erythrocytes coated with human immunoglobulin G (IgG) anti-D antibody (EA) as important in the inhibition of Ig synthesis in myeloma patients. Using monoclonal antibodies, two-color fluorescence studies, and flow cytometry, we characterized this EA cell as a Leu-1+ (cluster designation (CD) 5), Leu-12+ (CD 19), Leu-16+ (CD 20), B2+ (CD 21), Leu-14+ (CD 22), and HLA-DR+ B cell. The cell was negative for antibodies to Leu-2 (CD 8), Leu-3 (CD 4), Leu-4 (CD 3), Leu-5 (CD 2), Leu-7, Leu-8, Leu-11 (CD 16), Leu-M1 (CD 15), Leu-M3, and CALLA (CD 10). This profile is consistent with a Leu-1+ B cell and excludes a T cell, natural killer cell, and monocyte. Comparison of the relative role of these cells to the role of monocytes in the suppression of pokeweed mitogen-stimulated Ig synthesis was determined in serial studies on 19 myeloma patients. The mean (+/- SEM) percentage of inhibition of Ig synthesis by monocytes from stage I myeloma patients was 14 +/- 2.2%, from stage II patients was 37 +/- 3.5%, and from stage III patients was 51 +/- 4.7%. Inhibition of Ig synthesis by Leu-1+ EA cells was 46 +/- 1.5%, 48 +/- 1.6%, and 43 +/- 3.7% in stage I, II, and III patients, respectively. Immunosuppressive B cells are an important component of inhibition of Ig synthesis in the immunodeficiency of myeloma.     

Leu-1+ (CD5+) B cells. A major lymphoid subpopulation in human fetal spleen: phenotypic and functional studies

Examination of the cell surface phenotype of fetal splenic lymphocytes demonstrated a major, novel subpopulation of B cells that co-express Leu-1 (CD5) in addition to B cell differentiation antigens (Leu-1+ B cells). These cells are similar to some conventional B cells in that they express HLA-DR, Leu-12, and B1, as well as both immunoglobulin (Ig) M and IgD. They comprise 40 to 60% of total splenic B cells in the fetus but are infrequent in fetal liver and adult spleen. Fetal Leu-1+ B cells do not respond to pokeweed mitogen with either proliferation or Ig secretion, and in contrast to the murine counterpart, Ly-1 B cells, they do not constitutively produce Ig. Leu-1+ B cells were incapable of augmenting Ig production of Leu-1- B cells when suboptimal numbers of T cells were present; however, they did require the presence of T cells to secrete antibody. They do not cap either the CD5 protein or surface Ig. These cells are a unique subpopulation of fetal splenic B cells that do not function as conventional B cells. Their role in the humoral immune response is unknown. They may represent the normal stage of B cell development, which is reflected in the phenotype of B cell CLL cells.     

Lectin-dependent and anti-CD3 induced cytotoxicity are preferentially mediated by peripheral blood cytotoxic T lymphocytes expressing Leu-7 antigen

Monoclonal antibodies against the CD3 antigen and certain lectins can induce interleukin 2 dependent antigen-specific T cell clones to mediate non-antigen specific cytotoxicity. On the basis of this observation, we predicted that it may be possible to identify cytotoxic T lymphocytes (CTL) in peripheral blood without knowing the antigen specificity of these in vivo primed CTL. By using this strategy, peripheral blood lymphocytes were separated into low and high-density fractions on Percoll gradients and were tested for cytotoxic activity in the presence or absence of concanavalin A (Con A) or anti-Leu-4 antibody. Lectin-dependent cellular cytotoxicity (LDCC) and anti-CD3 induced cytotoxicity against both natural killer (NK)-insensitive and NK-sensitive targets were exclusively mediated by low-density CD3+ T lymphocytes. Additional studies indicated that low-density CD3+ T lymphocytes co-expressing Leu-7 antigen preferentially mediated this activity, although in some individuals, significant activity was also observed in the low-density T cells lacking Leu-7. In contrast, high-density CD3+ T lymphocytes and CD16+ (Leu-11+) NK cells (both Leu-7 and Leu-7+) did not mediate nonantigen-specific cytotoxicity under these conditions. The finding that NK cell-mediated cytotoxicity was unaffected by these lectins refutes the hypothesis that lectin-dependent cellular cytotoxicity is simply a result of effector and target agglutination. T cell-mediated cytotoxicity was both lectin and antibody specific. Phytohemagglutinin, Con A, and pokeweed mitogen induced cytolytic activity in the Leu-7+ T cells, whereas wheat germ agglutinin did not. Of the antibodies against T cell-associated differentiation antigens (anti-Leu-2,3,4, and 5), only anti-Leu-4 induced cytotoxicity. This anti-CD3-induced cytotoxicity was essentially completely inhibited by the presence of anti-LFA-1 or anti-CD2 monoclonal antibodies, implicating these molecules in the triggering process. A proportion of the CD3+, Leu-7+ CTL expressed HLA-DR antigens, indicating possible in vivo activation. Because previous clinical studies have indicated that lymphocytes with this phenotype may be elevated in clinical situations associated with immunosuppression and chronic viral infection, this unique subset of CD3+ T lymphocytes may represent a population of in vivo primed CTL possibly against viral antigens.     

Differential expression of ecto-5' nucleotidase activity by functionally and phenotypically distinct subpopulations of human Leu-2+/T8+ lymphocytes

Subsets of Leu-2+/T8+ cytotoxic/suppressor T lymphocytes were isolated by using various methods of purification and were investigated for expression of ecto-5' nucleotidase (5'NT) enzyme activity by radiochemical, cytochemical, and ultrastructural techniques. By using both the radiochemical and the cytochemical methods. T4-OKM1- cells displayed higher 5'NT activity in comparison with the entire T4- subpopulation. Analyses of the subpopulations of T4- (and predominantly Leu-2+) cells defined by the Leu-15 or Lyt-1 (9.3) monoclonal antibodies demonstrated that T4-Leu-15- and T4-Lyt-1+ cells displayed high 5'NT activity, whereas virtually no activity was present in T4-Leu-15+ and T4-Lyt-1-cells. At the ultrastructural level, the 5'NT reaction product was detected on the plasma membrane of a proportion of nongranular Leu-2+/T8+ lymphocytes, but no activity was found on cells with a granular lymphocyte (GL) morphology. 5'NT activity was also analyzed in peripheral blood mononuclear cells from one patient with expanded numbers of GL and two patients with GL leukemia. The enzymatic activity was significantly lower in these patients than in normal controls. This study provides new cytochemical evidence demonstrating the heterogeneity of Leu-2+/T8+ cells, and indicates that the population with the suppressor phenotype and function (Leu-15+/Lyt-1-, GL morphology) displays low or absent 5'NT activity, whereas the population composed of cytotoxic cell precursors (Leu-15-/Lyt-1+, nongranular morphology) has high 5'NT activity. Implications of these data for the interpretation of low 5'NT activity described in several immunodeficiency states and lymphoproliferative disorders are discussed.     

The relationship of CD16 (Leu-11) and Leu-19 (NKH-1) antigen expression on human peripheral blood NK cells and cytotoxic T lymphocytes

We examined the antigenic and functional characteristics of human peripheral blood lymphocytes that differentially express the CD16 (Leu-11) and Leu-19 (NKH-1) antigens. Leu-19 is a approximately 220,000 daltons protein expressed on approximately 15% of freshly isolated peripheral blood lymphocytes. Within the Leu-19+ subset, three distinct populations were identified: CD3-,CD16+,Leu-19+ cells; CD3+,CD16-,Leu-19+ cells; and CD3-,CD16-,Leu-19bright+ cells. Both the CD3+,CD16-,Leu-19+ and CD3-,CD16+,Leu-19+ populations mediated non-major histocompatibility complex (MHC)-restricted cytotoxicity against the NK-sensitive tumor cell K562 and were large granular lymphocytes. CD3-,CD16+,Leu-19+ NK cells were the most abundant (comprising approximately 10% of peripheral blood lymphocytes) and the most efficient cytotoxic effectors. The finding that CD3+,Leu 19+ lymphocytes mediated cytotoxicity against K562 unequivocally demonstrates that a unique subset of non-MHC-restricted cytotoxic CD3+ T lymphocytes are present in the peripheral blood of unprimed, normal individuals. However, CD3+,CD16-,Leu-19+ cells comprised less than 5% of peripheral blood lymphocytes, and the cytotoxic activity of this subset was significantly less than CD3-,CD16+,Leu-19+ NK cells. Most CD3+,Leu-19+ T cells co-expressed the CD2, CD8, and CD5 differentiation antigens. The antigenic and functional phenotype of peripheral blood CD3+,Leu-19+ cytotoxic T lymphocytes corresponds to the interleukin 2-dependent CD3+ cell lines that mediate non-MHC-restricted cytotoxicity against NK-sensitive tumor cell targets. A small population of Leu-19bright+ lymphocytes lacking both CD3 and CD16 was also observed. This population (comprising less than 2% of peripheral blood lymphocytes) contained both large agranular lymphocytes and large granular lymphocytes. CD3-,CD16-,Leu-19bright+ lymphocytes also mediate non-MHC-restricted cytotoxicity. The relationship of these CD3-CD16-,Leu-19bright+ lymphocytes to CD3+ T cells or CD16+ NK cells is unknown.     

Salivary gland lymphocytes in primary Sjogren's syndrome lack lymphocyte subsets defined by Leu-7 and Leu-11 antigens

Primary Sjogren's Syndrome (SS) is an autoimmune disease characterized by dry eyes and dry mouth due to lymphocytic infiltration of lacrimal and salivary glands. Biopsies of their salivary glands provided an opportunity to characterize the phenotypic and functional properties of inflammatory site lymphocytes. We found that the salivary gland lymphocytes (SGL) of SS patients differed from the peripheral blood lymphocytes of the same patients because: a) SGL lacked lymphocytes reactive with anti-Leu-7 and anti-Leu-11 monoclonal antibodies; b) SGL lacked natural killer (NK) activity; and c) SGL lacked the ability to suppress polyclonal B cell responses in the presence of complement fragment C3a, a function that requires the presence of Leu-7+ cells. These studies also showed that the SGL of SS patients differed from tonsillar lymph node (LN) lymphocytes of immunologically normal individuals because tonsillar LN contained Leu-7+ T cells, and tonsillar LN could suppress polyclonal B cell responses in the presence of the complement fragment C3a. The absence of this regulatory subset in the salivary glands of SS patients may contribute to pathogenesis, because these cells may be important in the suppression of polyclonal antibody synthesis and in the elimination of neoplastic or viral infected cells.     

The fine structure of HNK-1 (Leu7) positive cells

Summary The ultrastructural characteristics of HNK-1 (Leu7) positive cells, visualized with a peroxidase labelled anti-mouse IgM serum, were analysed. Our investigation demonstrates: 1) the majority of Leu7 positive cells has a low nuclear/cytoplasmic ratio (N/C), an irregular outline, a well developed smooth endoplasmic reticulum, parallel tubular arrays (PTA) and electron dense granules; 2) the minority of Leu7 positive cells has a high N/C, regular profiles and lacks electron dense granules. The presence of two distinct ultrastructural patterns within Leu7 positive cells may represent: 1) the expression of subsequent stages of cell differentiation; 2) two distinct Leu7 positive cell subpopulations.