Major expansions of select CD8+ subsets in acute Epstein-Barr virus infection: comparison with chronic human immunodeficiency virus disease

CD8+ lymphocyte phenotypes were characterized during acute Epstein-Barr virus (EBV) infection, and a comparison was made to previous studies of human immunodeficiency virus (HIV). This was of interest because CD8+ cells contribute to immunologic control of both infections, but the usual outcome of EBV infection is benign, whereas untreated HIV infection is fatal. During acute EBV infection, CD8+ cells expressed elevated levels of the activation antigens CD38 and HLA-DR, similar to that during chronic HIV infection. Within 16 weeks, when EBV latency is established, CD8+ cell activation had resolved. In contrast, activation persists in HIV infection. Expression of CD38 and HLA-DR on CD8+ cells could be a marker for ongoing viral replication in both infections. Other CD8+ cell alterations observed in this study of acute EBV infection included increases in both CD62L- and CD62L+ CD8+ cells and unique kinetics in the expansion of the CD57+CD8+ cell subset.

Local increase level of chondroitin sulfate induces changes in the rhombencephalic neural crest migration

Numerous studies suggest that chondroitin sulfate proteoglycan (CSPG) inhibits neural crest cells (NCC) migration at the trunk level. However, its action on the cephalic neural crest is not clear. To determine this action, we have microinjected 0.5 nl of different concentrations of chondroitin sulfate (CS) at the anterior rhombencephalon level in 9 stage chick embryos, as well as subgerminally administering beta-D-xyloside to 8 stage chick embryos. Beta-D-xyloside disrupts CSPG synthesis, producing an increase in CS free chains in several embryonal anlages. Chondroitin sulfate microinjected embryos and beta-D xyloside treated embryos were reincubated until attaining 12 stage. Results obtained for both experimental groups were similar. Immunoreactivity with HNK-1 antibody revealed that NCC did not migrate, remaining near the rhombencephalon dorsal wall; in addition, several NCC did not separate from the neural fold, becoming invaginated towards the rhombencephalon cavity. Our findings indicate that an increase in CS free chains in cephalic neural crest migratory routes not only disrupts their migration, but also impedes delamination and detachment of the rhombencephalic neuroepithelium NCC. These data suggest that the inhibitory action upon the neural crest migration attributed to CSPG may rest on its glycosaminoglycan (GAG). We cannot, however, rule out the possibility that increases in other GAGs apart from CS, may produce similar effects on neural crest migration.

Double staining of proteoglycans and the HNK-1 carbohydrate epitope in pseudoexfoliation material

PURPOSE

We combined the techniques of both immunogold and cupromeronic-blue staining with electron microscopy to investigate the possible relationship between proteoglycans and the HNK-1 carbohydrate epitope in pseudoexfoliation material.

METHODS

The anterior segment was obtained from an enucleated eye with pseudoexfoliation syndrome. After cupromeronic-blue staining, following the method of Scott, specimens were embedded in L. R. White resin. Ultrathin sections were incubated successively in primary monoclonal antibodies, and 10 nm gold-conjugated secondary antibody.

RESULTS

The present study showed simultaneous presence of the HNK-1 epitope and proteoglycans associated with zonular fibrils and pseudoexfoliation material on the posterior surface of the iris. The HNK-1 epitope was immunolocalized to the periphery of the pseudoexfoliation fibers, while cupromeronic blue-positive filaments bridged adjacent pseudoexfoliation fibers.

CONCLUSIONS

Proteoglycans and the HNK-1 epitope might play a substantial role in the formation of pseudoexfoliation material via their adhesive function. Proteoglycans probably do not directly bear the HNK-1 epitope in pseudoexfoliation material.

Pericellular deposition of basement membrane material in myxoid meningioma: immunohistochemical evidence for unbalanced production of type IV collagen and laminin

Myxoid meningioma seen in a 25-year-old man is presented. Histologically, Leu 7-positive meningotheliomatous tumor cells were embedded in the alcianophilic myxoid matrix. Characteristically, eosinophilic granular deposition was detected around the tumor cells and the boundary of tumor cells was not clearly defined. The pericellular deposits revealed the nature of the basement membrane with positive reactions by periodic acid-Schiff (PAS) sequence and immunostaining for type IV collagen, which is the major structural component of basement membrane. However, laminin, which is a non-collagenous glycoprotein of the basement membrane, was undetectable, and silver was not impregnated. Similar abnormal deposition of PAS-positive basement membrane-like material was observed in the myxoid stroma of a microcystic meningioma among 72 meningiomas additionally examined. The significance of the discrepant localization of immunoreactive type IV collagen and laminin is discussed.

Distribution of cells bearing the HNK-1 epitope in the human placenta

HNK-1 (Leu-7 antigen or CD57) is a unique carbohydrate moiety found in certain glycosphingolipids and several cell adhesion glycoproteins on the cell membrane. Previous studies have suggested that HNK-1 carbohydrates act as adhesive ligands in cell-cell interactions. Using a monoclonal antibody reactive to the HNK-1 moiety and an immunoperoxidase method on formalin-fixed paraffin-embedded tissue, the expression of the HNK-1 epitope in human placentae was confined to the intermediate trophoblast (IT) in trophoblastic columns. The number of HNK-1 immunoreactive IT cells increased from the proximal to the midportion of the trophoblastic column, and then disappeared at the junction of the column with the basal plate where IT infiltrates the endomyometrium and becomes extravillous IT. Neither cytotrophoblast nor syncytiotrophoblast reacted with the HNK-1 antibody. In hydatidiform moles, HNK-1 immunoreactivity was localized to areas that structurally resembled trophoblastic columns. In contrast, placental site trophoblastic tumours which do not contain structures analogous to trophoblastic columns did not express HNK-1 epitope. Expression of HNK-1 was only rarely observed in choriocarcinomas, being present in less than 5 per cent of trophoblastic cells in two of 13 cases. The murine placenta, which lacks trophoblastic columns, was negative for HNK-1. Thin-layer chromatography immunostaining demonstrated the HNK-1 reactive glycosphingolipids in placental lipid extracts, whereas Western blot analysis from placental protein extract failed to reveal detectable glycoproteins that demonstrated HNK-1 immunoreactivity. In conclusion, the specific localization of HNK-1 reactive glycosphingolipids in trophoblastic columns of the human placenta suggests that the HNK-1 moiety may play an important role in maintaining cohesion between intermediate trophoblastic cells in the trophoblastic columns thereby contributing to the structural integrity of the villi that anchor the placenta to the basal plate.

Parachordoma: a clinicopathologic and immunohistochemical study of four cases of an unusual soft tissue neoplasm

Four soft tissue tumors corresponding with the previously reported parachordoma are described. Three of the patients were men, and one was a woman, and their ages ranged from 14 to 53 years (mean age, 29). The tumors were located either superficially or within muscle, and, in one case, involved a tendon. Histologically, the tumors displayed whorls, nests, and pseudoglandular cords of uniform polygonal cells with eosinophilic, vacuolated cytoplasm, in a focally myxoid stroma. Transitions were seen between fascicles of ovoid-spindled cells, with scanty cytoplasm in a fibrous stroma, and, in one case, whorls of bland spindly cells were also present. Electron microscopy of one case showed cells with short interdigitating microvilli and ill-defined junctions. The principal cells in all cases were positive for S100 protein, Leu-7, keratin (CAM5.2), and epithelial membrane antigen (EMA). All tumors were negative with antibody AE1 and with antibodies to cytokeratins CK7 and CK19. No tumor displayed immunoreactivity for carcinoembryonic antigen (CEA), muscle specific actin (MSA), smooth muscle actin (SMA), desmin, glial fibrillary acid protein (GFAP), CD31, or CD34. Parachordoma appears to be an entity with clinical and pathological differences from chordoma, which has a different cytokeratin profile, behaves in a more aggressive fashion, and can dedifferentiate. The differential diagnosis includes myxoid chondrosarcoma, myoepithelial cell tumor, ossifying fibromyxoid tumor, and chondroid lipoma.

The HNK-1 epitope in the pseudophakic and aphakic eye and secondary cataract

PURPOSE

To search for changes in the presence and distribution of the cell-adhesion-related HNK-1 carbohydrate epitope after cataract extraction.

METHODS

Twenty-five pseudophakic and two aphakic human autopsy eyes and, for comparison, one anterior subcapsular cataract obtained at surgery were studied with monoclonal antibodies (MAbs) HNK-1 and NC-1 to the HNK-1 epitope using the avidin-biotinylated peroxidase complex method.

RESULTS

MAbs to the HNK-1 epitope constantly immunolabelled the inner connective tissue layer of the ciliary body in all pseudophakic and aphakic eyes studied. The distribution of the immunoreaction was similar to that reported for normal eyes. They also labelled the extracellular matrix in each of 18 plaques of secondary cataract on the posterior capsule, in each of 13 plaques at the rim of the capsular bag, and in the anterior subcapsular cataract. Bladder cells in each of 16 Soemmering's rings remained unlabelled.

CONCLUSION

The distribution of the HNK-1 epitope in the ciliary body does not appreciably change after cataract extraction, although the accommodative demand of the eye is altered. Its presence in an anterior subcapsular cataract suggests that the epitope may be locally produced by lens epithelial cells also in secondary cataract. The epitope is associated with cell adhesion and migration, both of which may play a role in the pathogenesis of secondary cataract.

Changing activation sequence in the embryonic chick heart. Implications for the development of the His-Purkinje system

In the mature heart, impulse propagation through the His-Purkinje system (HPS) is required for efficient ventricular contraction in an apex-to-base direction. However, the embryonic heart begins to contract as a myocardial tube without a specialized conduction system. To identify the developmental stage when the HPS begins to function, we mapped the ventricular depolarization sequence from microvolt-level electrograms recorded from embryonic myocardium using 50-micron extracellular electrodes, high-gain amplification, and signal-processing techniques. Analysis of left ventricular activation in 99 embryonic hearts revealed a transition in the activation sequence that was dependent on developmental stage. As the heart develops, a transition in the activation sequence occurred from the primitive base-to-apex pattern (in 20 of 33 hearts) at early stages (Hamburger-Hamilton stages 25 to 28) to the HPS-like apex-to-base pattern (12 of 17 hearts) late in development (stages 33 to 36). Immunohistological experiments (n = 10) also confirm that the expression pattern of two biochemical HPS markers changes in parallel with the change to the mature ventricular activation pattern. These data indicate that the ventricular activation sequence in the chick heart develops to a mature pattern at stages 29 to 31, suggesting that preferential conduction through the HPS begins shortly after ventricular septation is complete.

Numerical and functional characteristics of lymphocyte subsets in centenarians

The immune system in the aged is a very interesting subject for study. In this study, analysis was extended to extrathymic T cells as well as NK cells and "conventional" T cells (i.e., thymus-derived T cells) in terms of their constitution and function in both healthy and unhealthy centenarians. Middle-aged persons were used as controls. Healthy and unhealthy centenarians showed lower levels in the proportion and absolute number of lymphocytes. The major change in the constitution of lymphocyte subsets was increased levels in the proportion of NK cells (CD56+/CD57+) and extrathymic T cells (CD3+CD57+). Inversely, conventional T cells decreased in proportion and function (i.e., proliferative response to mitogen). Although NK cells increased in centenarians, NK activity by whole lymphocytes and the purified NK fraction decreased. The difference between healthy and unhealthy centenarians was small in all parameters, the only difference being a lower level of expression of CD56 antigens on CD57+ T cells in unhealthy centenarians. These results indicate that there is a major shift in lymphocyte population from conventional T cells to NK cells and extrathymic T cells with aging. Concerning the age-associated increases in CD56+ T and CD57+ T cells, these cells correspond to NK1+ T cells in mice.

Autopsy analysis of clinically unilateral exfoliation syndrome

PURPOSE

To study the pathogenesis of clinically unilateral exfoliation syndrome by localizing exfoliation deposits in involved and fellow eyes during autopsy.

METHODS

The formalin-fixed and paraffin-embedded involved and fellow eyes were obtained at autopsy from five patients (age range, 72 to 88 years) with clinically unilateral exfoliation. Exfoliation deposits were identified with monoclonal antibodies (mAb) HNK-1 and NC-1 to the HNK-1 carbohydrate epitope, and with five lectins (Bauhinia purpurea agglutinin, Concanavalin A, Lens culinaris agglutinin, Phaseolus vulgaris erythroagglutinin, and Ricinus communis agglutinin I) using the avidin-biotinylated peroxidase complex (ABC) method.

RESULTS

Marked exfoliation deposits in all involved eyes, and weak exfoliation deposits in one fellow eye were consistently detected in light microscopic, immunohistochemical, and lectin histochemical examinations. Similarly labeled deposits were present around a population of blood vessels of the iris in every involved and fellow eye. Particularly in fellow eyes, these subendothelial deposits were better visualized with mAbs to the HNK-1 epitope than they were with lectins. In the only fellow eye with early exfoliation, the reactivity around blood vessels was more conspicuous than the exfoliation deposits, whereas the reverse was true in the involved eyes.

CONCLUSIONS

Clinically unilateral exfoliation is asymmetric, rather than truly monocular. The findings in fellow eyes suggest that iris blood vessels become abnormal early in the process, even before exfoliation deposits are histopathologically seen in the posterior chamber. Marked asymmetry in exfoliation indicates an influence of modulating local factors that may be internal or external to the eye, and that also may be functional in bilateral exfoliation.

Expression of alphaB-crystallin in glia cells during lesional development in multiple sclerosis

The small heat shock protein alphaB-crystallin was recently identified as a dominant human T-cell antigen in myelin derived from multiple sclerosis (MS) patients. Using immunohistochemical techniques, oligodendrocytes as well as astrocytes in MS lesions were shown to express alphaB-crystallin. In the present study we examined the expression of alphaB-crystallin, human natural killer cell marker (HNK-1; as a marker for immature oligodendrocytes) and heat shock protein 60 (hsp60) in glia cells at different stages of MS lesion development i.e. in early active lesions, late active lesions and inactive lesions. The results demonstrate that already at the earliest stages of lesional development a subpopulation of oligodendrocytes express detectable levels of alphaB-crystallin. In active lesions about 5-10% of all oligodendrocytes were found to express alphaB-crystallin, whereas in inactive lesions the relative number of alphaB-crystallin-expressing oligodendrocytes was approximately tenfold less. For astrocytes the relative number of alphaB-crystallin-expressing cells was 40-50% for all three types of lesions. Also, alphaB-crystallin-expressing oligodendrocytes and astrocytes displayed different patterns of distribution in lesional areas. These data suggest different regulatory pathways for alphaB-crystallin expression in either type of glia cell. No correlation was found between expression patterns of HNK-1 and alphaB-crystallin indicating that the subpopulation of alphaB-crystallin-expressing oligodendrocytes consisted of both mature and immature oligodendrocytes. In addition, no correlation was found between expression of hsp60 and alphaB-crystallin in MS lesions suggesting different regulatory pathways for either hsp.

Immunohistochemical characterization of retinal glial cell changes in areas of vascular occlusion secondary to diabetic retinopathy

PURPOSE

To study changes in retinal glial cell components in areas of vascular occlusion secondary to diabetic retinopathy.

MATERIAL

The retina from ten eyes of six diabetic patients and from five eyes of five normal controls were studied for immunoreactivity to glial fibrillary acid protein and vimentin (glial cells), S-100 protein (perivascular glial cells), carbonic anhydrase isoenzyme II and CD-57 antigen (Müller cells), and CD-68 antigen (microglia).

RESULTS

The study showed increased immunoreactivity to S-100 protein, corresponding to perivascularly located glial cells in the retina from diabetic patients, except for areas of vascular occlusion where this immunoreactivity was absent. Furthermore, the material invading the lumen of former retinal vessels in areas of vascular occlusion showed immunoreactivity to CAH-II and CD-57, suggesting that this material represents ingrowth of retinal Müller cells.

CONCLUSIONS

The findings suggest that at least two types of changes in retinal glial cells are involved in the pathophysiology of diabetic retinopathy, i.e. 1) Reactive changes in the perivascular glial cells in the retina, and 2) Müller cell ingrowth into the former lumen of occluded retinal vessels.

The HNK-1 epitope and the elastic fiber system of the human ciliary body. An immunoelectron microscopic study

PURPOSE

To localize at the electron microscopic level the cell adhesion-related HNK-1 carbohydrate epitope in the inner connective tissue layer (ICTL) of the human ciliary body.

METHODS

Seven specimens representing the pars plicata (age range, 12 to 86 years) and three specimens representing the pars plana (age range, 29 to 71 years) of the ciliary body were sampled at death from eight normal human eyes. Three additional specimens from the pars plicata were taken from three eyes with exfoliation syndrome (age range, 78 to 81 years). All specimens were embedded in LR white resin and studied by postembedding immunogold labeling using two monoclonal antibodies (mAbs) HNK-1 and NC-1 in detecting the HNK-1 epitope.

RESULTS

In the ICTL of the pars plicata and the pars plana, mAbs HNK-1 and NC-1 constantly bound to the surface of fibroblast-like cells present in the subepithelial connective tissue matrix. The immunoreaction was localized along the cell membrane, both around the cell body and around its long, slender cytoplasmic processes. Long microfibrillar bundles, which consisted of approximately 10-nm thick microfibrils in close association with these subepithelial matrix cells and elastic fibers, were also labeled. The periphery of elastic fibers was likewise immunolabeled for the HNK-1 epitope. The reaction pattern was essentially the same, regardless of age and presence or absence of exfoliation syndrome.

CONCLUSIONS

At the ultrastructural level, the HNK-1 epitope in the ICTL is a common denominator to the subepithelial matrix cells, microfibrillar bundles, and elastic fibers. This suggests that the subepithelial matrix cells secrete this epitope, and that molecules hearing it may be involved in joining these connective tissue elements that structurally stabilize the ciliary body.

HNK-1 carbohydrate-mediated cell adhesion to laminin-1 is different from heparin-mediated and sulfatide-mediated cell adhesion

The sulfated HNK-1 carbohydrate present on glycolipids and on several neural recognition molecules has been shown to mediate the adhesion of murine small cerebellar neurons and astrocytes to the extracellular matrix molecule laminin-1. In this study, we characterized the binding of the HNK-1 carbohydrate to laminin-1 extracted from the Engelbreth-Holm-Swarm (EHS) sarcoma and distinguished it unequivocally from binding sites for other sulfated carbohydrates. Electron microscopic analysis of rotary shadowed complexes of laminin-1 and a HNK-1 neoglycoprotein revealed a major binding site on the G domain that comprises the C-terminal globule of the laminin alpha1 chain. The HNK-1 carbohydrate also interacted with placental laminin isoforms containing an alpha chain variant. It bound to the proteolytic laminin-1 fragment E8 comprising the domains G1-G3, but not to fragment E3 that carries the major heparin-binding site on domains G4-G5. No binding was observed to the short arm containing fragments E1XNd or P1. Binding studies with native or denatured laminin E8 fragments and proteolytic or recombinant fragments of the G domain localized the HNK-1 carbohydrate binding site to domain G2. The binding could be clearly distinguished from binding sites for other sulfated carbohydrates such as heparin and sulfatides. Further, the binding could not be abolished by reduction and alkylation or by urea treatment of laminin-1 and was independent of the native conformation of laminin-1 and of Ca2+. The G2 domain is also involved in the adhesion of HNK-1 carbohydrate expressing early postnatal cerebellar neurons and is different from heparin- and sulfatide-mediated cell adhesion to laminin-1. HNK-1 carbohydrate-mediated cell adhesion appears, however, to be dependent on the native conformation of laminin-1 indicating a more complex cellular recognition process.

HNK-1 epitope in the lens-ciliary zonular region in normal and pseudoexfoliative eyes. Immunohistochemistry and ultrastructure

OBJECTIVE

To determine the specific binding sites for the HNK-1 adhesion molecule epitope in the lens-ciliary zonular region in normal and pseudoexfoliative (PSX) eyes.

METHODS

Normal and PSX eyes and adjacent tissues from individuals aged 10 months to 89 years were investigated for the HNK-1 epitope by immunohistochemistry and immunogold electron microscopy.

RESULTS

Concentration of HNK-1 epitope was high in the anterior central lens capsule into old age, but it tapered earlier and progressively in the inner capsule and elsewhere. On zonular fibers, label was strongest at their lens and ciliary attachments and intense on related elastic microfibrils in adjacent ciliary stroma. Label was also strong on PSX fibers and above normal on PSX central capsule. In contrast, HNK-1 was absent on PSX aggregates in conjunctiva and skin and on normal elastic microfibrils in these tissues.

CONCLUSIONS

The prominent HNK-1 epitope in lens capsule and zonule has age- and site-specific variations that favor adhesive roles in each. The high density of epitope on ocular PSX material suggests an aberrant increase in expression that may contribute to adhesiveness of these aggregates, HNK-1 negativity on extraocular elastic microfibrils and PSX aggregates indicates a unique difference in composition of intraocular and extraocular elastic tissue, of potential significance for ocular function in aging and lens-dislocating diseases.

CD24, a mucin-type glycoprotein, is a ligand for P-selectin on human tumor cells

P-selectin (CD62P) is a Ca2+-dependent endogenous lectin that can be expressed by vascular endothelium and platelets. The major ligand for P-selectin on leukocytes is P-selectin glycoprotein ligand-1 (PSGL-1). P-selectin can also bind to carcinoma cells, but the nature of the ligand(s) on these cells is unknown. Here we investigated the P-selectin binding to a breast and a small cell lung carcinoma cell line that are negative for PSGL-1. We report that CD24, a mucin-type glycosylphosphatidylinositol-linked cell surface molecule on human neutrophils, pre B lymphocytes, and many tumors can promote binding to P-selectin. Latex beads coated with purified CD24 from the two carcinoma cell lines but also neutrophils could bind specifically to P-selectin-IgG. The binding was dependent on divalent cations and was abolished by treatment with O-sialoglycoprotein endopeptidase but not endoglycosidase F or sialidase. The beads were stained with a monoclonal antibody (MoAb) to CD57 (HNK-1 carbohydrate epitope) but did not react with MoAbs against the sialylLe(x/a) epitope. The carcinoma cells and CD24-beads derived from these cells could bind to activated platelets or P-selectin transfected Chinese hamster ovary cells (P-CHO) in a P-selectin-dependent manner and this binding was blocked by soluble CD24. Transfection of human adenocarcinoma cells with CD24 enhanced the P-selectin-dependent binding to activated platelets. Treatment of the carcinoma cells or the CD24 transfectant with phosphatidylinositol-specific phospholipase C reduced CD24 expression and P-selectin-IgG binding concomitantly. These results establish a role of CD24 as a novel ligand for P-selectin on tumor cells. The CD24/P-selectin binding pathway could be important in the dissimination of tumor cells by facilitating the interaction with platelets or endothelial cells.

PIG-A gene mutations in four Taiwanese patients with paroxysmal nocturnal haemoglobinuria following aplastic anaemia

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired haemolytic disorder caused by deficient biosynthesis of the glycosyl phosphatidylinositol (GPI) anchor in haemopoietic stem cells. PIG-A, an X-linked gene that participates in the first step of GPI-anchor synthesis, is responsible for PNH. Various abnormalities of the PIG-A gene have been demonstrated in all patients with PNH so far examined. In this study we characterized the somatic mutations in PIG-A gene in four Taiwanese patients with PNH. We identified five novel mutations in the PIG-A gene, three single nucleotide substitution mutations (-342, C-->G, codon 335, GGT-->AGT and codon 405, GCT-->GTT) and two frameshift mutations (codon 22, GGA-->G-A and codon 356, TGT-->TGTT) in the PIG-A gene. The -342 mutation was judged to be a polymorphism. Furthermore, three patients had previous clinicopathologic evidence which suggested aplastic anaemia (AA), before the development of PNH. One of these was found to have thrombocytopenia during follow-up. We suggest that the somatic PIG-A gene mutations highlight a subgroup of AA having a pathogenetic link with PNH.

L1/HNK-1 carbohydrate- and beta 1 integrin-dependent neural cell adhesion to laminin-1

We have shown recently that mouse small cerebellar neurons adhere to a short amino acid sequence of the G2 domain of the laminin alpha 1 chain via the cell surface-expressed HNK-1 carbohydrate. Therefore, we were interested in identifying glycoproteins carrying the HNK-1 carbohydrate at the cell surface of these neurons. Adhesion of small cerebellar neurons to laminin is partially dependent on Ca2+, Mn2+, and Mg2+, indicating the involvement of integrins, which were identified as beta 1, alpha 3, and alpha 6. They could be shown to bind to laminin by a beta 1-dependent adhesion mechanism. None of these subunits was found to carry the HNK-1 carbohydrate. HNK-1-immunoreactive glycoproteins were immunoprecipitated and shown to consist of predominantly one molecular species, which was identified as the neural cell recognition molecule L1. L1 was demonstrated to bind in a concentration-dependent and saturating manner to laminin. The binding could be partially inhibited by Fab fragments of monoclonal antibodies against the HNK-1 carbohydrate and against the Ig-like domains of L1. Furthermore, antibodies to the Ig-like domains of L1 and beta 1 integrin inhibited partially cell adhesion to laminin. Determination of the association of L1, beta 1 integrin, and the HNK-1 carbohydrate on the cell surface of live cerebellar neurons by antibody-induced patching and copatching revealed HNK-1 to be linked to L1, but less so to beta 1 integrin. However, only negligible association was found between L1 and beta 1 integrin. Furthermore, it could be shown that adhesion to laminin is mediated by L1/HNK-1- and beta 1 integrin-dependent mechanisms that act at least partially independent of each other.

HNK-1 antigens on uveal and cutaneous melanoma cell lines

The HNK-1 epitope has been associated with the metastatic behaviour of uveal melanomas. We characterized HNK-1 antigens on four human uveal (primary and metastatic) and two primary cutaneous melanoma cell lines by immunocytochemistry and Western blot analysis. We also determined the involvement of the HNK-1 epitope in cell-cell interactions on a matrigel layer. Three uveal melanoma cell lines (one primary and two metastatic) and one cutaneous melanoma cell line showed HNK-1 expression by immunocytochemistry. On matrigel, only the HNK-1-positive cutaneous melanoma cell line Bowes grew in a honeycomb-like structure which disappeared after adding HNK-1 antibodies to the culture medium. Immunoblot analysis of the primary uveal melanoma cell line EOM-3 revealed five HNK-1-positive protein bands with apparent molecular weights of 200, 160, 115, 95 and 75 kDa. The cutaneous melanoma cell line Bowes showed three HNK-1-positive protein bands with apparent molecular weights of 150, 135 and 90 kDa. This study shows that two uveal (primary and metastatic) and one primary cutaneous melanoma cell lines express HNK-1 antigens on immunoblot. Only in the HNK-1-positive cutaneous melanoma cell line Bowes did the HNK-1 epitope have a function in intercellular adhesion. Although the primary uveal melanoma cell line EOM-3 showed a similar HNK-1 immunoreactivity, we could not demonstrate HNK-1-mediated cell adhesion. On immunoblot, the two cell lines displayed different HNK-1 antigens, which may explain the difference in cell adhesion.

Human first-trimester placenta intra-arterial trophoblast cells express the neural cell adhesion molecule

The supposed influence of endometrial natural killer (NK) cells on the trophoblast invasion activities especially on intravasation of uteroplacental arteries in the non-pathogenic human first-trimester placenta was studied by means of immunohistochemistry. To identify extravillous trophoblast cells, smooth muscle cells, endothelia, endometrial glands, decidual stroma cells and endometrial NK cells, antibodies against cytokeratins, vimentin, smooth muscle cells, epithelium specific antigen and endothelial cells were employed. Furthermore, the immunohistochemical distribution patterns of CD56, CD57 and CD94 were studied and compared with the localization of invading trophoblast cells. Remodelling and dilatation of uteroplacental arteries starts before trophoblast cells can be found in the vicinity of the vessels. Nevertheless, subsequent trophoblast invasion of the arterial wall will lead to media destruction and intravasation only on focally restricted areas. This process is accompanied by the disappearance of endothelial cells and the immediate expression of the neural cell adhesion molecule (N-CAM, CD56) by intra-arterial trophoblast cells, which are eventually beginning to form intraluminal plugs. These findings led us to the conclusion that in the human pregnancy-induced physiological changes of the uteroplacental blood flow and the peripheral blood NK cell activity is not only, but also, due to the effect of CD56 expression by intra-arterial trophoblast cells.

The T-cell receptor repertoires expressed by CD4+ and CD4- large granular lymphocytes derived from the same patients suggest the persistent action of an immune-mediated selection process

The lymphoproliferative syndrome with large granular lymphocytes (LGL) is an heterogeneous disorder of unknown etiology. The analysis of T-cell receptor (TCR) genes rearrangements has shown that, in most cases, the disease is associated with clonal proliferation of CD8+CD57+ LGL. However, the putative neoplastic nature of these expansions remains questionable because clonal proliferations of CD8+ cells have recently been found also in physiologic conditions. To obtain more precise information on the mechanisms responsible for LGL expansions, we decided to compare the molecular characteristics of TCRBV chains expressed by LGL with different phenotype and function, but derived from the same patients. To this end, we characterized, at the molecular level, the TCR repertoires of fractionated T-cell populations of two unusual patients with concurrent expansions of CD4+CD57+ and CD4-CD57+ LGL. Our results show that the dominant TCRBV chains expressed by the different CD4+ and CD4- LGL populations were strictly oligoclonal. However, the molecular characteristics of the dominant V-D-J rearrangements also imply that the selection of these clones was not due to a neoplastic event. Rather, our data suggest that these particular LGL proliferations can be ascribed to a chronic T-cell-mediated immune response that involves recognition by the engaged TCR of antigens that are not necessarily presented to immune system in the classical major histocompatibility complex-restricted pathway.

Immunohistochemical evidence for increased numbers of 'classic' CD57+ natural killer cells in the endometrium of women suffering spontaneous early pregnancy loss

Despite increasing knowledge about the cell populations that exist in the decidualized endometrium in normal early human pregnancy, little is known about the decidual leukocyte populations in women suffering spontaneous early pregnancy loss. Decidual leukocytes were investigated in 40 cases of spontaneous abortion using a panel of monoclonal antibodies specific for leukocytes, macrophages, T cells, B cells and 'classic' CD57(+) natural killer (NK) cells and an avidin-biotin peroxidase immunohistochemical technique. Endometrial granulated lymphocytes (eGL), the predominant decidual leukocyte population in the first trimester of normal human pregnancy, were demonstrated with the phloxine-tartrazine stain. There were significantly fewer leukocytes in decidua in spontaneous abortion, but the numbers of eGL, macrophages and T cells did not differ significantly between normal and pathological pregnancies. eGL and macrophages accounted for a greater proportion of the decidual leukocyte population in spontaneous abortion. Of the 40 spontaneous abortion cases, 20 had significantly increased numbers of 'classic' CD57(+) NK cells when compared with normal human pregnancy. A proportion of spontaneous abortions may occur because of increased 'classic' CD57(+) NK cell numbers in the decidua, which could become activated by local cytokines to attack the trophoblast.

Selective loss of myelin-associated glycoprotein from myelin correlates with anti-MAG antibody titre in demyelinating paraproteinaemic polyneuropathy

The IgM monoclonal autoantibodies of patients with demyelinating paraproteinaemic polyneuropathy recognize a carbohydrate structure present on both myelin-associated glycoprotein (MAG) and protein zero (P0). These autoantibodies are sufficient to cause the disease but the mechanism of demyelination remains unclear. We have analysed nerve biopsies from eight patients with polyneuropathy and anti-MAG antibodies by quantitative immunohistochemistry and find a concordant pattern of reduced expression of myelin markers with the loss of myelinated fibres. We report here novel features of this disease, in particular a selective lack of detectable MAG in a large proportion of myelinated-fibres containing P0, myelin basic protein (MBP) and periaxin. There is also an inverse correlation of the distribution of MAG in peripheral nerve myelin with the serum anti-MAG antibody titres but no correlation of these titres with the loss of myelinated fibres. Double immunofluorescence staining of paraproteinaemic polyneuropathy (PPN) nerves shows anti-MAG IgM deposited on the periphery of myelinated fibres associated with or lacking MAG staining. These data suggest that the binding of anti-MAG antibodies to MAG and/or other myelin component(s) results in MAG downregulation and may have an essential role in the molecular mechanisms leading to demyelination and partial regeneration in this disease.

The enigma of CD57+CD28- T cell expansion--anergy or activation?

Expansion of a CD57+CD8+ T lymphocyte subset has been reported in HIV and human cytomegalovirus (HCMV) infection. Almost all of these T cells lack CD28 expression. While CD28- cells are often associated with anergy, some authors believe their expansion in HIV infection precipitates immunodeficiency. We studied 15 randomly chosen patients with immune activation and observed that CD57+CD28- T cell expansion may occur in various conditions and to the same degree as in HIV infection without resulting in immunodeficiency. Triple colour flow cytometry also revealed that the CD57 and CD28 antigens are coexpressed in only 3% of CD8+ T cells, irrespective of the underlying condition, so that almost all CD57+CD8+ cells are always CD28-. Analysis of Fas (CD95) expression with respect to CD28 expression on CD4+ and CD8+ T cells from 10 additional patients indicated no increased commitment to apoptosis in CD28- T cells. Semiquantitative polymerase chain reaction (PCR) comparing CD28+ and CD28-CD8+ T cells with respect to cytokine gene expression (tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-1beta) in five renal transplant patients with expansion of the CD57+ subset detected no cytokine gene expression deficit in CD28- T cells. A direct association of increased proportions of CD57+CD28-CD8+ T cells with immunodeficiency/anergy is disputed.