Expression and regulation of CD5 on in vitro activated human B cells

The T cell-associated antigen CD5 has been shown to play an important role in the regulation of T cell activation. Monoclonal antibodies directed against CD5 upregulate helper function, and induce interleukin 2 (IL2) production by mature T cells as well as thymocytes. CD5 is also expressed on subsets of B cells associated with autoantibody production, and CD5+ B cells are present in increased numbers in patients with rheumatoid arthritis and systemic lupus erythematosis. More recently CD5 has been found to be present on human B lymphocytes following in vitro activation with phorbol myristate acetate. To date a similar functional role for CD5 has not to date been demonstrated for B cells. In this study we have shown that structurally similar CD5 molecules are present on activated B cells and T cells. In addition, CD5 on both stimulated B cells and T cells is phosphorylated, which may be important in the function of CD5 following activation. CD5 protein or mRNA was not detected on unstimulated splenic B cells depleted of any CD5+ cells. To investigate the control of CD5 expression, we examined a series of cytokines either alone or in combination for their effect on the induction of CD5. CD5 expression was specifically inhibited by IL4 but not by the other cytokines tested. This inhibition was very specific as IL4 did not inhibit the expression of other B cell activation antigens including CD25, B5, T9 and CD23 as well as the pan-B cell antigen CD20. The addition of other cytokines did not increase or reverse the inhibition of CD5 expression by IL4. This inhibition was demonstrated by immunofluorescence and flow cytometric analysis. Immunoprecipitation studies of 125I-labeled activated B cells demonstrated that there was a decrease in cell surface CD5 protein, and not simply inhibition of expression of a particular epitope. Northern blot analysis demonstrated that the expression of CD5 mRNA was markedly inhibited in the presence of IL4, whereas the induction of the protooncogene c-myb was unaffected. This suggests that IL4 inhibits CD5 protein expression on activated B cells by reducing the amount of CD5 mRNA transcription or increasing the degradation of CD5 mRNA. The role of the T cell-derived lymphokine IL4 in regulating CD5 expression may be important in the disease states characterized by increased numbers of CD5+ B cells.

Specific overproduction of very late antigen 1 integrin in two human neuroblastoma cell lines selected for resistance to detachment by an Arg-Gly-Asp-containing synthetic peptide

Very late antigen (VLA) 1 is a member of the family of integral plasma-membrane glycoproteins known as integrins. It is a heterodimer composed of an alpha subunit of Mr 200,000, noncovalently associated with a beta subunit of Mr 110,000 which is shared by other VLA molecules (VLA-2-5). Unlike most of the other VLA proteins which have been shown to be receptors for various extracellular matrix proteins, the ligand for VLA-1 is unknown. Utilizing polyclonal antisera against the human fibronectin receptor as well as alpha subunit-specific monoclonal antibodies and cDNA probes, we have been able to demonstrate that in two human neuroblastoma cell lines, IMR-32 and SK-N-SH, the common beta subunit is associated with alpha 1, alpha 2, alpha 3, and alpha 5 subunits. By culturing these two cell lines in the presence of a synthetic peptide, Gly-Arg-Gly-Asp-Ser-Pro, which contains the Arg-Gly-Asp cell attachment promotion tripeptide, we have isolated variant cell lines resistant to the detachment effects of this peptide. Peptide-resistant SK-N-SH and IMR-32 neuroblastoma cells exhibit weaker attachment to type I collagen and laminin, but a similar level of attachment to fibronectin as compared to the parental cells. Although the peptide-resistant variant cell lines proliferate at a rate similar to that of the parental cell lines, they stably overproduce (up to 20-fold) the alpha 1 subunit (VLA-1) specifically; and in the IMR-32 variant cells, the common beta 1 subunit is also overproduced. The level of expression of alpha 2 and alpha 3 subunits, however, is considerably reduced and that of the alpha 5 subunit is unchanged relative to the parental cells. These data suggest that the expression of integrin alpha subunits can be regulated differentially and independently of the beta subunit and that the VLA-1 heterodimer has an important function in mediating Arg-Gly-Asp-dependent cell adhesion or other phenotypic properties in human neuroblastoma cells.

Human interleukin 4 down-regulates the surface expression of CD5 on normal and leukemic B cells

CD5 is a pan-T cell antigen which is expressed on a minor subset of normal B lymphocytes and on most chronic lymphocytic leukemia B cells (B-CLL). In this study, it is demonstrated that interleukin (IL) 4 down-regulates the surface expression of CD5 on tonsil B cells and B-CLL cells, but not on T cells. IL 4 inhibits both the spontaneous and the phorbol myristate acetate (PMA)-induced hyperexpression of CD5 on tonsil B cells. In contrast, IL 4 only suppresses the PMA-induced hyperexpression of CD5 on B-CLL, whereas the spontaneous CD5 expression is essentially unaffected. The IL 4 concentrations required to down-regulate CD5 are the same as those required to up-regulate CD23. The IL 4-mediated down-regulation of CD5 is an intrinsic property of this IL, since an anti-IL 4-neutralizing antiserum blocks this effect. Interferon (IFN)-gamma, which inhibits the IL 4 induced CD23 expression, does not block the IL 4-induced down-regulation of CD5. Recombinant IL 1 alpha, IL 2, IL 3, IL 5, IL 6, tumor necrosis factor (TNF)-alpha, IFN-gamma and granulocyte macrophage colony-stimulating factor neither inhibit nor stimulate CD5 expression on B cells, therefore suggesting that the capacity to down-regulate CD5 expression on B cells is specific to IL 4.

CD1-positive epidermal Langerhans cells in skin reactions to autologous peripheral-blood-derived mononuclear cells in leprosy patients

A comparison was made on the characteristics of the infiltrates, the number and distribution of CD1-positive epidermal Langerhans cells (LC) at the sites of skin reaction induced by autologous peripheral-blood-derived mononuclear cells (PBMC) in leprosy patients. Clinically and histologically, the skin reaction was well expressed in tuberculoid patients as compared to lepromatous patients, erythema nodosum leprosum (ENL) patients and contacts. The quantum of lymphocytes in the infiltrates was maximal in the tuberculoid patients and it was minimal in lepromatous and ENL patients. The number and distribution of LC in the tuberculoid patients was significantly higher in the PBMC-inoculated sites as compared to control sites over 24 h. In contrast, no difference in the number and distribution of LC was noticed in the lepromatous and ENL patients. These observations indicate that the lymphocytes of tuberculoid patients in contrast to lepromatous leprosy patients are capable of sustenance in the local micro-environments of the skin and an effective interaction may be possible between LC and PBMC.

In vitro modulation of leucocyte-function-associated antigen-1 expression on two leukemic cell lines

Leukocyte-function-associated antigen-1 (LFA-1) expression on two widespread tumor cell lines: K562 (an erythroleukemia) and MOLT-4 (a T leukemia), was investigated using two monoclonal antibodies specific for the alpha chain of this surface antigen, and flow cytometry analysis. When K562 cells are in the exponential phase of growth, they display very low levels of LFA-1. By contrast, cells from the plateau phase exhibit a strong labelling, which disappears rapidly when they are allowed to resume division by changing the culture medium. Using the same experimental conditions, we failed to detect any LFA-1 expression on MOLT-4 cells. However, after stimulation of these cells by phorbol myristate acetate, we observed a significant labelling, which occurred within 2 days of treatment. The LFA-1 expression disappears progressively after removal of the phorbol ester. From these results it may be concluded that (a) LFA-1 expression can vary considerably according to the culture conditions, (b) the expression of this antigen on the surface of non-expressing variants can be induced by phorbol ester, and (c) in both cases, the change in expression can be reversed completely by replacing the culture medium or by removing phorbol myristate acetate from it.

Fc and complement receptor (CR1 and CR3) expression on neonatal human polymorphonuclear leukocytes

Fc gamma receptor III (Fc gamma RIII) and complement receptors (CR1 and CR3) were examined on polymorphonuclear leukocytes (PMN) from neonatal cord blood and adult blood using monoclonal antibodies directed against these receptors. Receptor expression was determined by flow cytometry. Fc gamma RIII, CR1 and CR3 expression was examined in whole blood at 4 degrees C, at 37 degrees C with or without stimulation with the chemotactic peptide f-met-leu-phe, and on PMN isolated by Ficoll-Hypaque centrifugation and dextran sedimentation. There was no significant difference between adult and cord PMN in the percent of cells which expressed Fc gamma RIII, CR1 and CR3 when examined in whole blood at 4 or 37 degrees C, or following stimulation with f-met-leu-phe. The percentage of PMN expressing CR1 and CR3 was lower on cord PMN compared to adult PMN when these cells were examined following Ficoll-Hypaque centrifugation and dextran sedimentation. The mean peak fluorescence of PMN which stained positively for CR1 and CR3 increased following f-met-leu-phe treatment of whole blood from adults and neonates. Since neonatal cord PMN were capable of upregulating complement receptors in response to chemotactic factors these results do not explain the increased susceptibility to infection exhibited by neonates.

Expression of haematopoietic progenitor cell-associated antigen BI-3C5/CD34 in leukemia

The expression of progenitor cell-associated antigen CD34, defined with monoclonal antibody BI-3C5, was investigated in cells from 109 patients with leukaemia. No reactivity was found in chronic leukaemias, whereas 31% of acute myelogenous leukaemia (AML) and most non-T, non-B acute lymphoblastic leukaemia (ALL) expressed CD34. Examples of BI-3C5+ AML included M1 and M2 FAB types only; all but one were myeloperoxidase positive. In combination with pan-myeloid markers, BI-3C5 is useful for identification of immature myeloid cells.

Structural and partial amino acid sequence analysis of the human hemopoietic progenitor cell antigen CD34

Monoclonal antibodies of the CD34 class all recognize a monomeric cell surface antigen of approximately Mr 110,000 which is selectively expressed on human hemopoietic progenitor cells. This structure can be readily surface-labeled with [125I]actoperoxidase and by periodate-[3H]borohydride, but it labels only weakly with [35S]methionine, [35Sl]cysteine, 3H-amino acids, or 3H-mannose, even after prolonged labeling periods. However, the antigen is more efficiently labeled by [3H]glucosamine. Lectin binding studies, sensitivity to certain glycosidases, and gel filtration analysis of glycans released by alkaline hydrolysis indicate that this glycoprotein contains several complex-type N-linked glycans as well as several highly sialylated O-linked glycans. Western blotting experiments show that various CD34 antibodies fail to efficiently detect desialylated and/or de-N-glycosylated forms of the antigen. Experiments involving the use of tunicamycin, together with metabolic labeling studies, strongly suggest that this structure "turns over" very slowly in vivo. The CD34 antigen is not detectably labeled by 32P-phosphate in vivo, nor are immune complexes containing it associated with phosphokinase activity in vitro. Sequential immunoprecipitation and Western blotting studies indicate that this antigen is not a member of the leukosialin/sialophorin family despite the fact that these molecules share several structural similarities. Partial amino acid analysis of highly purified CD34 antigen revealed no significant sequence similarity with any previously described structures.

Gamma interferon augments Fc gamma receptor-mediated dengue virus infection of human monocytic cells

It has been reported that anti-dengue antibodies at subneutralizing concentrations augment dengue virus infection of monocytic cells. This is due to the increased uptake of dengue virus in the form of virus-antibody complexes by cells via Fc gamma receptors. We analyzed the effects of recombinant human gamma interferon (rIFN-gamma) on dengue virus infection of human monocytic cells. U937 cells, a human monocytic cell line, were infected with dengue virus in the form of virus-antibody complexes after rIFN-gamma treatment. Pretreatment of U937 cells with rIFN-gamma resulted in a significant increase in the number of dengue virus-infected cells and in the yield of infectious virus. rIFN-gamma did not augment dengue virus infection when cells were infected with virus in the absence of anti-dengue antibodies. Gamma interferon (IFN-gamma) produced by peripheral blood lymphocytes from dengue-immune donors after in vitro stimulation with dengue antigens also augmented dengue virus infection of U937 cells. IFN-gamma did not augment dengue virus infections when cells were infected with virus in the presence of F(ab')2 prepared from anti-dengue immunoglobulin G. Human immunoglobulin inhibited IFN-gamma-induced augmentation. IFN-gamma increased the number of Fc gamma receptors on U937 cells. The increase in the percentage of dengue antigen-positive cells correlated with the increase in the number of Fc gamma receptors after rIFN-gamma treatment. These results indicate that IFN-gamma-induced augmentation of dengue virus infection is Fc gamma receptor mediated. Based on these results we conclude that IFN-gamma increases the number of Fc gamma receptors and that this leads to an augmented uptake of dengue virus in the form of dengue virus-antibody complexes, which results in augmented dengue virus infection.

Immortalization of cloned mouse splenic macrophages with a retrovirus containing the v-raf/mil and v-myc oncogenes

The recombinant retrovirus J2, which contains the v-raf/mil and v-myc oncogenes, was used to immortalize mouse splenic macrophages that had been cloned in soft agar. When added to freshly harvested colonies, J2 failed to yield cell lines but it immortalized up to 30% of the clones if they had been maintained for at least 4 months in medium containing colony-stimulating factor 1 (CSF-1). All of the cell lines grew in agar in a CSF-1-independent manner, and they produced tumors in nude and syngeneic mice. The cell lines were judged to be macrophage based on morphological criteria and because they secreted lysozyme, were phagocytic for antibody-coated particles, and expressed both the Mac-1 antigen and the CSF-1 receptor. The cell lines could be divided into three groups based on their expression of Ia and their ability to present an antigen to a T-cell hybridoma. The majority of the lines did not constitutively express Ia or present antigen, but a lymphokine did induce Ia in all of the lines, with most of them also acquiring antigen-presenting activity. However, a small proportion of lymphokine-treated lines continued to lack antigen-presenting activity despite their ability to express Ia. The third and smallest group of cell lines constitutively expressed both Ia and antigen-presenting activity. These results show that the J2 recombinant retrovirus is a useful means of immortalizing functionally distinct populations of cloned splenic macrophages.

Expression of differentiation antigens within human mammary tumours is related to response to endocrine therapy and survival

Human mammary tumours which are histologically well differentiated are more likely to synthesize receptors for estrogen (ER) and progesterone (PR) and to respond to systemic endocrine therapy. The aim of this study was to explore the relationship between differentiation, receptors and endocrine responsiveness in more detail by relating the expression of putative differentiation antigens within tumours to ER, PR and response to treatment. Sections of the primary tumours of 160 patients with advanced evaluable breast cancer were immunostained with 2 monoclonal antibodies (MAbs) (HMFG1 and HMFG2) raised against putative differentiation antigens found on the membranes which surround the milk fat globule. Tumours were highly heterogeneous with respect to antigen expression. However, the number of cells which expressed the antigens was highly correlated with ER and PR concentrations and with response to endocrine therapy. In tumours where greater than or equal to 20% of cells expressed the antigen recognized by HMFG1, 73% responded to endocrine therapy; this was similar to the response predicted by ER (67%) and PR (73%). Expression of HMFG1 was correlated with survival from the start of endocrine therapy (p less than 0.0001) to the same degree as ER and PR. Patients with tumours which expressed ER, PR and HMFG1 had the highest response rate (87%) and survival (median 49 months); the response in tumours which expressed none of these phenotypes was 13% and the median survival of these patients was 9 months. These results suggest that cells which express differentiation antigens also express ER and PR. Differentiated cells within mammary tumours may therefore be the target cells for systemic hormone, and also the source of factors which control tumour growth.

Expression and function of a CD5 cDNA in human and murine T cells

In order to define the function of the CD 5 (T1, Leu 1, Tp 67 in the human; Ly-1 in the mouse) molecule, a cDNA clone of human CD 5 was expressed in a CD5-deficient Jurkat cell line and in a murine T cell hybridoma. A Jurkat subclone (Jurkat 9.9) produced interleukin 2 (IL 2) in response to anti-CD 3 monoclonal antibody (mAb) cross-linked to solid support. IL 2 production was enhanced by co-culture with the anti-CD 5 mAb OKT 1. A CD 5-deficient mutant clone Jurkat 1.15 was generated by treatment with ethyl methanesulfonate followed by selection with anti-CD 5 mAb plus complement. Jurkat 1.15 did not demonstrate enhancement of IL 2 production by OKT 1 in the presence of cross-linked anti-CD 3 mAb. A cDNA encoding human CD 5 was introduced into a defective retrovirus which was used to infect Jurkat 1.15. A Jurkat clone stably expressing CD 5 was established. In response to OKT 1, a rise in intracellular calcium was observed in both the parent Jurkat 9.9 and the CD 5+ infectant but not in the CD 5- mutant or a G 418- resistant control. Furthermore, expression of CD 5 restored the augmentation of IL 2 production by OKT 1 in response to cross-linked anti-CD 3 mAb. A murine T cell hybridoma By 155.16 which produces IL 2 in response to HLA-DR antigens was also infected with the CD 5-recombinant retrovirus and three stable CD 5+ infectants were generated. These hybridomas showed enhancement of IL 2 production by stimulation with OKT 1 in the presence of suboptimal concentrations of soluble anti-murine CD 3 mAb. These results provide further evidence that CD 5 provides a co-stimulatory signal for T cell activation.

Induction of Fc (IgG) receptor(s) by simian cytomegaloviruses in human embryonic lung fibroblasts

Human embryonic lung (HEL) fibroblasts infected with simian cytomegalovirus (SCMV) were found to bind nonspecifically to the Fc portion of human immunoglobulin (Ig) G (IgG). Binding of IgG to SCMV-infected HEL fibroblasts, but not to uninfected HEL cells, was visualized as cytoplasmic fluorescence by the indirect immunofluorescence test, regardless of the presence of anti-CMV antibodies. The receptor(s) reacted with the IgG class of different species, but not with IgM and IgA. The purified Fc fragment reacted with the receptor(s), but the Fab fragment reacted poorly. The reaction was blocked by pretreatment of infected cells with the Fc fragment, but was not blocked with the Fab fragment. The appearance of the Fc receptor(s) required RNA and protein synthesis, whereas a requirement for DNA synthesis remains to be answered by a more sensitive assay. The development of the Fc receptor(s) was inhibited by 2-deoxy-D-glucose, thus indicating that the Fc receptor(s) may be a glycoprotein(s). The Fc receptor(s) was induced by all strains of SCMV tested so far. These included one laboratory strain (GR2757), four fresh isolates from primary kidney cell cultures of African green monkeys, and four fresh isolates from the salivary glands of the Macaca monkeys captured from the wild in Japan.