Proliferation of IL-2 activated lymphocytes preferably occurs in aggregates by cells expressing the CD57 antigen.

Aggregates of lymphocytes were investigated in long-term cultures of IL-2 stimulated peripheral blood mononuclear cells. Cells in clusters formed broad contact areas where coated pits and vesicles were often detectable. Proliferating cells were preferably found in aggregates indicating that the cell clusters represent proliferation centres in which cell division may be promoted by accessory signal transduction mediated by the close cell-to-cell contact. In bulk cultures CD57+ cells yielded increased proliferation capacity compared to CD57- cells. In addition, CD57+ cells were preferably localized in aggregates where they occupied the same position at the periphery of the clusters than the proliferating cells, suggesting that both cell types may be identical. It is discussed that the CD57 antigen represents a differentiation marker which is upregulated when CD57- cells start to proliferate assisted in cell aggregates.

Development of four donor-specific phenotypes in human long-term lymphokine-activated killer cell cultures.

A series of 62 lymphokine-activated killer cell (LAK) cultures from 44 different donors was investigated for the distribution of various CD markers during a cultivation period of 3 weeks. Great differences in the phenotypic pattern were found between different donors, but similar changes of the subset pattern of various donors allowed a classification of the LAK cultures into four distinct LAK types. LAK type 1 was characterised by low numbers of CD3+ cells and high values for CD56+ cells. In LAK type 2 cultures gamma/delta TCR+ cells extensively proliferated, whereas in LAK type 3 cultures the CD57 and CD8 values increased considerably. LAK type 4 cultures did not show any of these characteristics. The resulting phenotype of a LAK culture was donor-specific, as LAK cultures established from the same peripheral blood mononuclear cells (PBMC), fresh or after cryopreservation, or from PBMC obtained from the same donor at different venous punctures, always developed the same phenotype. A clear correlation between phenotype and killing activity could only be found for LAK type 1 cultures, which always developed high lytic activity. Long-term IL-2 stimulation induced high levels of perforin-positive cells in LAK cultures but the perforin content did not correlate with the cytotoxicity. The transcription pattern for various cytokines only varied slightly between the cultures. Messenger RNA for granulocyte/macrophage- colony-stimulating factor, interferon gamma, tumour necrosis factor alpha, interleukin-4 (IL-4) and IL-5 were found in almost all cultures during the entire cultivation period, whereas mRNA for IL-2 was never detected. Most variations in the transcription pattern were observed for IL-6 and IL-7. However, no correlation could be found between the endogenous cytokine production and the phenotype or lytic activity of the LAK cultures. Further studies are required to determine the factors that cause lymphocyte subsets from a specific donor to proliferate preferentially under long-term IL-2 stimulation.

Heterogeneous binding and killing behaviour of human gamma/delta-TCR+ lymphokine-activated killer cells against K562 and Daudi cells.

Effector-target conjugates, formed by coincubation of lymphokine-activated killer (LAK) cells with either K562 or Daudi cells, were separated from single cells by Percoll sedimentation. The occurrence of various CD molecules (CD3, CD56, CD57, CD16, gamma/delta-TCR) was compared in both fractions. Only LAK cells expressing the gamma/delta T cell receptor (TCR) were found in a significantly increased percentage in fractions containing conjugates indicating that gamma/delta-TCR+ LAK cells were preferably bound to target cells at the time of separation. In order to determine whether gamma/delta-TCR+ LAK cells also show a preferred killing activity against the targets, cultures enriched with or depleted of gamma/delta-TCR+ cells were established. Against K562 cells, gamma/delta-TCR(+)-enriched cultures showed a greatly reduced killing activity compared to LAK bulk cultures or cultures depleted of gamma/delta-TCR+ cells. Using Daudi cells as targets the enriched fraction revealed a slightly increased killing activity compared to bulk cultures or depleted fractions. Preincubation of gamma/delta-TCR+ LAK cells with anti-gamma/delta or anti-CD3 mAb resulted in a distinct increase of the killing activity against K562 cells, but in only a slightly enhanced activity against Daudi cells. It is postulated that gamma/delta-TCR+ LAK cells use the same adhesion mechanism for both targets but that only Daudi cells express a specific ligand for the gamma/delta-TCR. Occupation of the gamma/delta-TCR/CD3 complex by mAb, however, seems to substitute for the absent epitope on K562 cells by eliciting stimulatory signals in gamma/delta-TCR+LAK cells which, in combination with the binding stimulus, trigger cytolytic activity.

Ultrastructure of cell mediated cytotoxicity.

Contact dependent cell mediated cytotoxicity has been found to be executed by lymphocytes, macrophages, and even granulocytes. Cytotoxic effector cells of the lymphatic lineage are divided into cytotoxic T lymphocytes (CTL), mediating MHC related cytotoxicity, and in effectors mediating non-MHC restricted cytotoxicity such as natural killer (NK) cells, T lymphocytes displaying NK-like activity and lymphokine activated killer (LAK) cells. In morphologic studies these cells are hardly to be distinguished: they all show features of large granular lymphocytes (LGLs), which are characterized by a low nuclear to cytoplasmic ratio and azurophilic granules. Ultrastructurally lysosomal granules, showing an electron dense core that is either surrounded by numerous small vesicles or by a small electron translucent halo, have been found. Pore-forming proteins such as perforin, as well as serine esterases and proteoglycans have been pointed out in these granules. Specialties are parallel tubular arrays (PTA) in NK cells and nuclear inclusion bodies in LAK cells. Morphologically two types of killing event may be distinguished. In one way membrane lesions develop at the surface of target cells upon binding of effector cells and in advanced stages of cytolysis the target cells are surrounded by a completely disintegrated membrane. The nuclei, however, show only minor changes. In the other way, called apoptosis, the cell membrane of the targets remains intact, but the nucleus and cell organelles very early disintegrate intracellularly. Whether these morphologically different types of cell killing correspond to the functionally different pathways of cell mediated cytotoxicity remains to be resolved.

Malignant haemangioendothelioma of the thyroid, immunohistochemical evidence of heterogeneity.

26 cases of malignant haemangioendothelioma (MHE) of the thyroid gland were investigated immunohistochemically with the endothelial marker UEA-1 lectin and the panepithelial marker Lu-5. The results were compared with the results of staining for factor VIII-related antigen in the same cases observed in a previous study of Pfaltz et al. The 26 cases were classified on light microscopic grounds without reference to the immunohistochemical results as classical MHE (15 cases) and borderline cases intermediate between MHE and undifferentiated carcinoma (11 cases). 7 of the 15 classical MHE revealed one or both of the vascular markers, but did not express the epithelial marker. One case showed no staining and another reacted only with Lu-5. Vascular and epithelial markers were found in 6 cases of the 15 classical MHE and in 2 of the 11 borderline cases. These findings indicate that MHE of the thyroid may represent a heterogeneous group of lesions. Tumours positive only for endothelial markers strongly support the hypothesis that MHE is of endothelial origin, whereas tumours which reacted only to the epithelial marker may be undifferentiated carcinomas. Cases with both epithelial and endothelial features on immunohistochemical investigation may represent either tumours in which the malignant cells are in transition from epithelial to mesenchymal differentiation as suggested by Eckert et al. or are tumours of malignant endothelial cells with epithelial differentiation particularly of their cytoskeleton.

Solid cell nests (SCN) in Hashimoto's thyroiditis.

In Hashimoto's thyroiditis squamous metaplasia has been described by several authors. Such foci resemble the so-called solid cell nests (SCN) of the thyroid, epidermoid structures thought to be remnants of the fourth endodermal pouch. These cell nests can be identified by their particular histological appearances and by their positive reaction with polyclonal anti-CEA. In order to study this phenomenon more closely we examined the H & E-stained histological sections of 79 cases of Hashimoto's thyroiditis systematically. In 39 cases cell nests of three different types could be demonstrated: Small groups of elongated cells organized into solid epidermoid clusters, larger epithelial cells forming solid nests or similar epithelial but cystic structures. 29 of these 39 cases were further investigated immunohistochemically for the presence of thyroglobulin, CEA (polyclonal antiserum) and calcitonin. The first type of cell nest did not show any CEA-positivity, whereas the second and third type contained CEA-positive cells in 73% of the cases. In no cases were thyroglobulin- or calcitonin-positive cells identified in these epidermoid foci. Slide series of 25 of the 39 cases have further been investigated immunohistochemically for the presence of CEA (monoclonal antiserum), chromogranin, keratin and the epitope for Lu-5. In these additional series foci of epidermoid cells could be demonstrated in up to 15 of the 25 cases. They showed a positive reaction for the monoclonal CEA antiserum in only 3 of 15 cases, for anti-keratin in 5 of 14 cases and for Lu-5 in 13 of 15 cases. Immunoreactions for chromogranin were negative in all cases. Our findings suggest that epidermoid cell nests in Hashimoto's thyroiditis more closely resemble SCN than foci of follicular cell squamous metaplasia.

Effects of washing and gel filtration on the ultrastructure of human platelets.

The ultrastructure of washed and gel-filtered platelets has been examined by scanning- and transmission-electron microscopy. Three different washing procedures previously established for functional studies have been employed. Each washing method resulted in typical morphologic alterations of the platelets. Gel filtration of platelet-rich plasma appeared less harmful than washing. Specimens fixed immediately after elution contained numerous platelets with typical shape changes which were restored almost completely after incubation at 37 degrees C. Our study emphasizes the need for cautious interpretation of results obtained with separated platelets and mandates morphologic controls for such experiments.

Morphologic alterations of blood cells in the impedance aggregometer.

The scanning (SEM) and transmission (TEM) electron microscopic appearance of blood cells was studied in correlation with the aggregometer tracing recorded after activation of whole blood samples by collagen or ADP. Early morphologic alterations of platelets characterized by the formation of marginal pseudopods and bulbous protrusions were not indicated by the aggregometer. The initial increase in impedance was caused by the attachment of platelets displaying typical shape change morphology at the surface of the electrode wires joint with collagenous fibrils in collagen activated specimens. During further increase in impedance, aggregates were detectable in the blood suspension and at the electrode, the number and size of which increased up to the maximal extension of the aggregometer tracing. Using low doses of ADP (2-3 microM), dissociation of aggregates in the blood suspension was detectable by SEM, which was not recorded by the aggregometer tracing indicating further limitation of the impedance aggregometer. In collagen activated samples, platelet aggregates were covered by PMN and monocytes that in TEM displayed distinct phagocytosis of platelet fragments and fibrin masses. In ADP specimens, activation of leukocytes was only rarely detectable. The detection of mixed aggregates may be important for further employment of the impedance aggregometer in the diagnosis of hematologic diseases.