Identity of Leu-19 (CD56) leukocyte differentiation antigen and neural cell adhesion molecule

Human trophoblast and JEG choriocarcinoma cells are sensitive to lysis by IL-2-stimulated decidual NK cells

Freshly isolated decidual large granular lymphocytes (LGL) show natural killer (NK) activity against K562 cells but not against normal human trophoblast. We now show that these decidual LGL proliferate in vitro in response to recombinant interleukin-2 (rIL-2) and that these rIL-2-stimulated cells acquire a broad cytolytic potential that is characteristic of lymphokine-activated killer (LAK) cells. Both fetal fibroblasts and JEG-3 choriocarcinoma cells are resistant to lysis by freshly isolated decidual effectors but are readily killed by IL-2-stimulated decidual LGL. The ability to kill these target cells is acquired after only 18 hr exposure to rIL-2. rIL-2-activated decidual LGL also kill cultured normal trophoblast cells but much lower levels of cytolysis were seen even after the effectors had been stimulated with rIL-2 for 4-6 days. The preferential killing of malignant over normal human trophoblast cells raises questions about the potential role of IL-2-activated decidual LGL in the control of unduly invasive or malignant trophoblast populations in vivo.

Expression of various isoforms of neural cell adhesive molecules and their highly polysialylated counterparts in diseased human muscles

Antibodies directed against neural cell adhesive molecules (NCAM) and in particular a monoclonal antibody recognizing polysialylated isoforms, were used to characterize the expression of these molecules in normal and diseased human muscles. Normal subjects as well as patients with inflammatory, dystrophic and denervating diseases were examined. By immunohistochemistry the main observations were (1) satellite cells expressed the non-sialylated form of NCAMs; (2) regenerative fibers strikingly expressed NCAMs and their sialylated isoforms both on membranes and in the cytoplasm; (3) in denervated muscles, fibers in atrophic groups and some fibers in acute denervation expressed NCAMs on their membrane but not the highly sialylated form; (4) finally, some fibers in myotonic dystrophy and fibers with rimmed vacuoles also expressed NCAMs. Biochemical approaches, using enzymes such as endoglycosidase N and phosphatidylinositol phospholipase C combined with immunoblot analysis allowed visualization of the nature of the expressed isoforms. We have shown that non activated cells, i.e. satellite cells and denervated fibers do not express polysialylated NCAMs. This post-translational modification may be only observed in activated or regenerating fibers. This would parallel the sequence of NCAM expression occurring in normal myogenic pathways.

Cell populations in the human early pregnancy decidua: natural killer activity and response to interleukin-2 of CD56-positive large granular lymphocytes

Large granular lymphocytes (LGL) have been shown previously to be the most abundant cell type in the first trimester human decidua. Purified populations of decidual LGL were prepared by flow cytometry of cell dispersions labelled with NKH1 (CD56), an antibody specific for peripheral blood LGL, and the functional properties of CD56-positive cells, CD56-negative and unsorted decidual cells compared. Both CD56-positive cells and unsorted decidual cells have cytotoxic activity against the natural killer (NK) cell target K562 which was weak compared with that of peripheral blood mononuclear cells (PBMC). The CD56-negative cells had no cytotoxic activity against K562. All three decidual cell populations proliferated in response to recombinant human interleukin-2 (rIL-2), but none produced detectable levels of IL-2 in culture. When unsorted decidual cells were cultured for 7 days in rIL-2 the proportion of CD56-positive cells increased and NK activity against K562 was augmented. The NK activity of purified CD56-positive decidual cells was also augmented by culturing in rIL-2. The potential role of decidual LGL in regulating the development of the semi-allogeneic placenta is discussed.

CD4+ and CD56+ acute monoblastic leukemia

We report here a patient with acute monoblastic leukemia whose leukemia cells had CD4 (T4) and CD56 (NKH-1) antigens, in addition to CD36 (OKM5) antigen. The leukemia cells did not have NK or ADCC activities. They showed no rearrangements of immunoglobulin heavy (IgH) chain and T cell receptor (TCR)-beta chain genes, indicating that the leukemia cells were nonlymphoid. The presence of this case suggests that leukemia cells could be originated from monocytes with NK-associated antigen without IgH or TCR rearrangements.

Lysis of myotubes by alloreactive cytotoxic T cells and natural killer cells. Relevance to myoblast transplantation

The aim of this study was to investigate the susceptibility of human myotubes to lysis by the two major types of cytotoxic effector cells, CD3+CD8+ cytotoxic T cells (CTL) and CD16+CD56+ natural killer (NK) cells. The myoblasts preparations used as target cells were greater than 90% pure as assessed by immunostaining with the Leu19 monoclonal antibody (MAb) that cross-reacts with the neural cell adhesion molecule N-CAM. Allospecific CTL lines were generated from mixed lymphocyte cultures, and freshly isolated allogeneic and autologous peripheral blood cells were used as a source of NK cells. The cytotoxicity was observed under phase optics and by immunoelectron microscopy, and was quantitated with a chromium release assay. Myotubes were efficiently killed by allospecific CTL and by autologous and allogeneic NK cells. The killing by CTL was inhibited with an anti-class I HLA MAb, and the killing by NK cells was inhibited by depleting peripheral blood cells of CD16+ cells with anti-CD16 MAb and complement. The results have important implications for myoblast transplantation, an experimental therapy of muscular dystrophy.

Leukocyte-cell adhesion: a molecular process fundamental in leukocyte physiology

Leukocyte-cell adhesion is a form of physical contact characterized by fast (firm) stickiness between the cells. To analyze the biology and molecular basis of this process, an adhesion-specific assay was developed: the phorbol ester-induced aggregation of human lymphocytes. This rapid and antigen-independent intercellular adhesion requires cellular metabolism, an intact cytoskeleton and extracellular divalent cations, and is mediated by preformed cell-surface proteins referred to as CAMs. Phorbol ester also induces aggregation of monocytes and granulocytes, as well as adhesion of T lymphocytes to either B cells or monocytes and of the leukocytes to vascular endothelial cells. By using the adhesion-specific assay and blocking monoclonal antibodies, several CAMs have been identified, namely the Leu-CAM family (CD11a-c/CD18) and ICAM-1 (CD54). The Leu-CAM family is composed of Leu-CAMa (CD11a/CD18), Leu-CAMb (CD11b/CD18) and Leu-CAMc (CD11c/CD18), three glycoprotein heterodimers made of a common beta-chain and distinct alpha-chains. ICAM-1 is an adhesive ligand for Leu-CAMa. Expression and use of the various CAMs is selective in different types of leukocytes. The Leu-CAMs have been purified and partially characterized. CD18, whose gene is on human chromosome 21, contains 5-6 N-linked complex-type oligosaccharides, and CD11 binds Ca++. Another adhesion pathway is mediated by CD2 and CD58. CD2, a glycoprotein selectively expressed by T cells, is a receptor for CD58, a cell-surface adhesive ligand with broad tissue distribution. Antibodies to the latter CAMs do not block the phorbol ester-induced lymphocyte aggregation. Adhesion is involved in a large variety of leukocyte functions. Anti-Leu-CAM antibodies block induction of IL-2 production and lymphocyte proliferation. Lymphocyte-mediated cytotoxicity is also inhibited. Endogenous NK and LAK cells use Leu-CAMs, ICAM-1 and CD2, and sometimes RGD receptors, to bind and kill tumor cells. Endogenous compounds such as H2O2 and LTB4 also induce Leu-CAM-dependent adhesion in monocytoid cells and granulocytes, respectively, and degranulation of the latter cells is enhanced by the adhesion process. Homologous CAMs have been identified in rabbit and mouse. In in vivo studies in the former species, anti-Leu-CAM antibodies block adhesion of leukocytes to vascular endothelium and thereby their migration into extravascular tissues. The antibodies thus inhibit granulocyte accumulation and plasma leakage in inflammatory lesions, and induce lympho- and granulocytosis, indicating that cell-adhesion contributes to the distribution of leukocytes in the body.(ABSTRACT TRUNCATED AT 400 WORDS)

Heterogeneity of human natural killer cells in the spleen

Natural killer cells have an important role in tumour and viral defence and immunoregulation. In the present study the pan-NK cell monoclonal antibody NKH1 was utilized to study the heterogeneity of NK cells in the human spleen. Using one and two colour analysis it could be demonstrated that the majority of NKH1+ NK cells are located in the red pulp and marginal zone whereas only a minor subset is found in the lymph follicles. In the red pulp, NK cells resemble those of peripheral blood in terms of function and phenotype. In contrast, the few NK cells in the lymph follicles are mostly NKH1+, CD2- and CD16- and thus express a unique phenotype. The analysis of tissue distribution provides a basis for further studies on NK cell kinetics and differentiation.

Involvement of CD56 (NKH-1/Leu-19 antigen) as an adhesion molecule in natural killer-target cell interaction

The CD56 differentiation antigen, recognized by anti-Leu-19 and NKH-1 mAbs, is a 200-220-kD glycoprotein that is expressed predominantly on human NK cells and a minor subset of T lymphocytes mediating MHC-unrestricted cytotoxicity. The recent finding that CD56 is an isoform of the neural cell adhesion molecule (N-CAM) prompted us to examine the adhesive function of CD56 in the NK-target cell interaction. Synergistic inhibitory effects of anti-CD56 mAbs with anti-LFA-1 and/or anti-LFA-3 mAbs were demonstrated on NK cell-mediated cytotoxicity and on NK cell binding to target cells only when the target cells also express CD56. These findings indicate that CD56 on NK cells can serve as the third pathway of cell adhesion other than those mediated by the CD2/LFA-3 and LFA-1/ICAM-1 interactions, and is involved in NK cell cytotoxicity when interacting with the cells bearing N-CAM.

Clonal evidence for the induction of NKH1 on activated human thymocytes. Functional changes associated with antigen expression

Freshly isolated human thymocytes lack the NKH1 antigen and the ability to lyse target cells without major histocompatibility complex restriction. Short-term culture of human thymocytes in interleukin (IL) 2 results in the generation of non-major histocompatibility complex-restricted effector cells, all of which express NKH1. The mechanism by which these cells appear in culture has yet to be elucidated. In the present studies, we developed thymocyte clones and performed a molecular analysis of T cell receptor gene rearrangements to demonstrate that the expression of NKH1 antigen is induced on the surface of NKH1- thymocytes in the presence of IL2. In addition, we were able to show that the NKH1+ fraction consistently displayed an increased proliferative response to similar concentrations of IL2 when compared to NKH1- cells, for both clonal and polyclonal populations of thymocytes. Taken together, these studies demonstrate that the initial appearance of the NKH1 antigen following thymocyte culture in the presence of IL2 results from the induction of NKH1 expression on NKH1- thymocytes, while the subsequent predominance of this cell type also results from an enhanced proliferative response to IL2 which coincides with NKH1 expression.