Immunologic Mechanisms in Psoriasis

The demonstration of activated T lymphocytes, HLA-DR+ I-CAM 1+, gamma IP-10+ keratinocytes, and increased levels of lymphokines in active plaques suggests that immunologic mechanisms may play a role in the pathogenesis of psoriasis. Epidermal hyperplasia and inflammation in psoriasis may be linked by those cytokines many of which are produced by both keratinocytes and leukocytes. Epidermal acanthosis and keratinocyte mitoses have been observed in delayed-type hypersensitivity reactions and after the intradermal injection of gamma interferon. Gamma interferon and its induced proteins have been demonstrated in active psoriatic plaques. Increased levels of the keratinocyte autocrine cytokines, transforming growth factor (TGF)-alpha and interleukin (IL)-6, have been detected in active plaques. The apparent overexpression of IL-6 in hyperplastic psoriatic tissue may explain features of psoriasis that link keratinocyte proliferation with immune activation and tissue inflammation. Both IL-6 and gamma interferon increased TGF-alpha expression in normal cultured keratinocytes. Cytokines produced during immune activation and other inflammatory processes may lead to epidermal hyperplasia.

Detection of the interferon-gamma-induced protein 10 in psoriasiform dermatitis of acquired immunodeficiency syndrome

Interferon-gamma-induced protein 10 is a 10-kd protein produced by human keratinocytes following an exposure to interferon gamma. Keratinocytes within psoriatic plaques and within delayed-type hypersensitivity reactions have been shown to stain strongly with an affinity-purified rabbit antibody prepared against interferon-gamma-induced protein 10, suggesting a possible role for interferon gamma in the production of the lesions. A psoriasiform eruption has been seen in patients with acquired immunodeficiency syndrome (AIDS). Its severity appears to correlate with the degree of immunodeficiency in the early stages of AIDS. We stained 10 lesions of psoriasiform dermatitis of AIDS with the anti-interferon-gamma-induced protein 10 antibody using immunoperoxidase techniques. As controls, we studied 10 lesions of non-AIDS psoriasis, six lesions of seborrheic dermatitis with psoriasiform hyperplasia, one lesion of lichen simplex chronicus, and four biopsy specimens of normal skin from patients with AIDS. In addition, normal skin specimens taken from patients with AIDS and human immunodeficiency virus-negative patients at time of autopsy were examined. An identical, strong and diffuse staining pattern was seen in all cases of psoriasiform dermatitis of AIDS, non-AIDS psoriasis, seborrheic dermatitis, and lichen simplex chronicus. The specimens of normal skin showed only weak basal layer staining with anti-interferon-gamma-induced protein 10. Thus, the presence of interferon-gamma-induced protein 10 in keratinocytes was associated with psoriasiform hyperplasia and could be detected in both AIDS-associated and classic psoriasis.

Role of growth factors, cytokines, and their receptors in the pathogenesis of psoriasis

Psoriasis is characterized by epidermal hyperplasia, altered epidermal maturation, and local accumulation of acute and chronic inflammatory cells. Keratinocyte hyperplasia in psoriasis may be explained in part by overproduction of growth factors or cytokines which stimulate epidermal proliferation and by altered metabolism of growth-factor receptors in affected skin. Psoriatic epidermis displays overproduction of TGF-alpha and interleukin-6 (IL-6), factors produced by keratinocytes and other cell types in psoriatic skin. TGF-alpha and IL-6 are mitogens for normal human keratinocytes and act via specific receptors. The TGF-alpha receptor (EGF receptor) is overexpressed in psoriatic epithelium and its altered expression could be caused in part by gamma interferon which prevents normal receptor down-regulation in response to EGF binding. Several phenotypic features of the psoriatic keratinocyte, including growth activation and expression of HLA-DR, gamma-IP-10, ICAM-1, and other molecules, are best explained as resulting from the combined effects of TGF-alpha, IL-6, and gamma interferon (and possibly other cytokines) on epidermal keratinocytes. The multiple histologic features of psoriasis, including epidermal hyperplasia and accumulation of acute and chronic inflammatory cells, may be mediated by defined growth factors and cytokines that are produced in psoriatic skin and affect the function of diverse cell types.

Occlusive hydrocolloid dressings decrease keratinocyte population growth fraction and clinical scale and skin thickness in active psoriatic plaques

Clinical studies suggest a therapeutic role for occlusion in the treatment of psoriasis. Previous studies, using multiparameter RNA/DNA flow cytometric analysis of epidermal suspensions obtained from active plaques, demonstrated increased keratinocyte growth fraction which reversed with successful medical treatment. Because keratinocyte growth fraction reflected disease activity, it was used in this study in addition to clinical evaluations in order to determine the efficacy of occlusion in the treatment of psoriatic plaques. In each of 9 patients, scale, skin thickness and erythema were compared in one occluded and one control plaque using an analog scale. Both scale and skin thickness, but not erythema, were decreased after 2 weeks of occlusion. However after 10 weeks, no additional differences were seen when compared with assessments made after 2 weeks, suggesting that the benefits of occlusive therapy occurred early. After 10 weeks of occlusion, the keratinocyte growth fraction was significantly decreased in occluded plaques. This study demonstrates that occlusion plays a synergistic role with other therapeutic modalities in ameliorating psoriatic plaques.

Recessive dystrophic epidermolysis bullosa skin displays a chronic growth-activated immunophenotype. Implications for carcinogenesis

Epidermolysis bullosa represents a grouping of inherited skin diseases characterized by epidermal fragility and frequently wounded skin. The recessive dystrophic subtype of epidermolysis bullosa (RDEB) is characterized by extensive dermal scarring after healing of repeated epidermal injuries and by an unusually high incidence of squamous cell carcinoma occurring in chronically wounded skin. In contrast, the simplex form of epidermolysis bullosa usually heals without scarring and does not predispose to malignant neoplasms of the skin. The differences in scarring and the neoplastic potential of these two forms of epidermolysis bullosa prompted us to investigate growth activation and differentiation characteristics in epidermal keratinocytes in individuals with these disorders. The expression of filaggrin, involucrin, cytokeratins, and the growth activation marker psi-3 was examined by immunohistochemistry in skin biopsy specimens from four individuals with epidermolysis bullosa simplex and six individuals with RDEB. Previous experiments using this technique have demonstrated that these antibodies are good markers for identifying growth-activated keratinocytes in wounded and hyperplastic epidermis. All biopsy specimens of healed wounds in skin from patients with RDEB showed epidermis that reacted with antibodies to filaggrin, involucrin, specific cytokeratins, and psi-3 in a growth-activated pattern. This growth-activated phenotype was maintained in keratinocytes from previously wounded skin that had been healed for more than 2 years. The RDEB growth-activated phenotype detected by immunohistochemistry was not associated with microscopically detectable epidermal hyperplasia. In contrast, all cases of epidermolysis bullosa simplex examined showed an epidermal phenotype similar to that of keratinocytes in normal skin. Thus, healing with dermal scar formation in RDEB is associated with a persistent growth-activated immunophenotype of epidermal keratinocytes. This chronic growth activation state or failure of cells to differentiate in a normal fashion may be directly linked to the high incidence of squamous cell cancers in individuals with RDEB.

Interleukin 6 is expressed in high levels in psoriatic skin and stimulates proliferation of cultured human keratinocytes

Psoriasis is a common papulosquamous skin disease. The histopathology is characterized by epidermal hyperplasia and inflammation. Recent studies suggest that keratinocyte proliferation and inflammation in psoriasis are manifestations of the same underlying pathological process. Interleukin 6 (IL-6), a cytokine that is a major mediator of the host response to tissue injury and infection, is produced by both keratinocytes and leukocytes in culture. IL-6 expression was studied in psoriatic plaques by immunoperoxidase staining with two different polyclonal anti-recombinant IL-6 antisera and by in situ nucleic acid hybridization with IL-6 cRNA probes. Epidermal and dermal cells in active psoriatic plaques from 35 psoriasis patients stained heavily for IL-6 as compared with nonlesional skin and with plaques after treatment with antimetabolic and antiinflammatory agents. Absorption of the anti-recombinant IL-6 antisera with purified fibroblast-derived IL-6 or with recombinant IL-6, but not bovine serum albumin, removed the immunostaining. Increased levels of IL-6 were detected in the plasma of patients with active psoriasis (mean 3 ng/ml) by using two different bioassays. IL-6 production by proliferating keratinocytes was suggested by IL-6-specific immunostaining in cultured normal and psoriatic keratinocytes and by the detection of mRNA specific for IL-6 in psoriatic epidermis by in situ hybridization. IL-6 stimulated the proliferation of cultured, normal human keratinocytes as assessed by two different assays. Thus, IL-6 could directly contribute to the epidermal hyperplasia seen in psoriatic epithelium as well as affect the function of dermal inflammatory cells.

A functionally unique anti-CD3 monoclonal antibody cross-reactive with basal keratinocytes

Monoclonal antibodies (mAb) 147, 446, and 454 each recognize different epitopes of CD3. The CD3 epitope recognized by mAb 446 is functionally unique for the T cell. In contrast to mAb 147 and 454, mAb 446 induces modulation of surface CD3 with delayed kinetics and, hence, is impaired in inducing a refractory state in the T cell to subsequent anti-CD3-induced helper function. MAb 446 (but not other anti-CD3 mAb, including mAb 147, 454, OKT3, and anti-Leu4) recognizes a cytoplasmic determinant within basal keratinocytes. Extraction of keratinocytes with nonionic detergent and 2 M NaCl abolished subsequent staining with mAb 446 but enhanced subsequent staining with anti-keratin mAb, suggesting that this cross-reactive determinant is not keratin. Immunoprecipitation of internally labeled keratinocytes with the anti-CD3 mAb 147 and 446 failed to reveal specific bands, whereas these same mAb immunoprecipitated specific bands from internally labeled CD3+ Jurkat cells corresponding to previously identified CD3 subunits, suggesting that the cross-reactive determinant in keratinocytes is also not CD3. The cross-reactivity is not species specific, in that mAb 446 stained a mouse keratinocyte line, nor is it absolutely keratinocyte specific, in that mAb 446 stained one of the two nonkeratinocyte human epithelial cell lines tested. This study raises the possibility that perturbation of unique CD3 epitopes may have unique effects on T cell surface events and subsequent activation and function.

Detection of a gamma interferon-induced protein IP-10 in psoriatic plaques

The pathologic features of psoriatic plaques are inflammation and increased epidermal turnover. IP-10, a cytokine the expression of which is induced by gamma-interferon, is a member of a family of soluble mediators with inflammatory and growth-promoting activities. IP-10 protein was detected in keratinocytes and the dermal infiltrate from active psoriatic plaques using an affinity-purified rabbit anti-IP-10 antibody in immunoperoxidase studies. Successful treatment of active plaques decreased IP-10 expression in plaques. These results were corroborated by Northern blot analysis with an IP-10 cDNA probe. We have previously detected activated T cells and HLA-DR keratinocytes in active psoriatic plaques. Since IP-10 is detected in delayed cellular immune responses, the present study further points to the role of ongoing cellular immune responses in the pathogenesis of psoriasis.

Immunologic mechanisms in psoriasis

This review presents evidence for the immunopathogenesis of psoriasis. T lymphocytes with human lymphocyte antigen (HLA)-DR molecules and receptors for interleukin 2 were found in the dermis of psoriatic plaques, suggesting the presence of activated T cells in these lesions. Keratinocytes in active plaques demonstrated HLA-DR molecules on their surfaces. These immunologic abnormalities were reversible with medical therapy. Keratinocyte HLA-DR expression was associated with an increased incidence of psoriatic arthritis. We propose that HLA-DR + keratinocytes and Langerhans cells in plaques could activate dermal T cells directly in an autologous mixed leucocyte/epithelial cell reaction. Alternatively, they could present an unknown autologous or exogenous antigen to T lymphocytes. T cell activation would then lead to the release of mediators of inflammation, and possibly of epidermal growth factors. This hypothesis also provides an explanation for the chronicity of psoriasis. Most of the therapies used to treat psoriasis suppress cellular immune function and inflammation. These include ultraviolet irradiation, cyclosporine, corticosteroids, methotrexate, anthralin, and retinoids.

A patient with lepromatous leprosy and anticytoskeletal antibodies

Sera from 34 patients with lepromatous leprosy were screened for the presence of autoantibodies by indirect immunofluorescence using two epithelial cell lines, PTK2 and HEp2, as substrates. Indirect immunofluorescence staining of both substrates with the serum of a patient with lepromatous leprosy revealed a cytoplasmic intermediate filament staining pattern. After exposure of PTK2 cells to colchicine, the filaments collapsed into thick perinuclear coils, confirming the presence of intermediate filament reactivity. Immunofluorescence of rat fibroblasts with the same serum also revealed an intermediate filamentous staining pattern. Human keratinocytes exposed to the patient's serum revealed a diffuse cytoplasmic staining pattern. Our study suggests the presence of autoantibodies to cytoskeletal intermediate filaments or to molecules associated with vimentin and possibly keratin subunit proteins in the serum of a patient with lepromatous leprosy.

Detection of transforming growth factor alpha in normal, malignant, and hyperproliferative human keratinocytes

Transforming growth factor alpha (TGF-alpha) is a 50-amino acid peptide, previously demonstrated only in transformed cell lines and human tumors, which is structurally homologous to epidermal growth factor (EGF). TGF-alpha expression in keratinocytes from normal individuals, patients with psoriasis, and patients with malignant skin diseases was investigated using an mAb raised against synthetic human TGF-alpha. mAb A1.5 reacted with TGF-alpha, but not EGF, in a sensitive ELISA. Keratinocytes in eight nodular basal cell carcinomas, one morpheic basal cell carcinoma, and one squamous cell carcinoma demonstrated intense membranous immunoperoxidase staining with mAb A1.5. Of even greater interest was the observation that the overlying normal epidermis, as well as the epidermis from five normal skin specimens, were stained by the mAb. Keratinocytes in plaques from 18 psoriasis patients were more intensely stained than those from normal skin. Cultured normal keratinocytes demonstrated membranous staining with mAb A1.5. Absorption of mAb A1.5 with synthetic human TGF-alpha completely removed the reactivity of mAb A1.5 with both basal cell tumors and normal epidermis. The demonstration of TGF-alpha in normal keratinocytes suggests that it plays a role in normal keratinocyte growth, wound healing, and in the pathogenesis of acanthosis.

Marked increase in the frequency of psoriatic arthritis in psoriasis patients with HLA-DR+ keratinocytes

Immunocytochemical studies with a monoclonal anti-HLA-DR antibody were performed on skin sections and keratinocyte (KTC) suspensions obtained from suction blisters of active psoriatic plaques. HLA-DR+ KTCs were found in the plaques of 23 of 38 patients with active psoriasis. Of these 23, 16 had clinical findings typical of psoriatic arthritis (PA); none of the 15 patients who lacked HLA-DR+ KTCs had PA. Although KTC HLA-DR expression was more prevalent in patients with severe skin disease, 7 of the 23 patients with HLA-DR+ KTCs in active psoriatic plaques had mild skin disease; 4 of these 7 had PA. Nail pitting or duration of skin disease did not account for increased incidence of PA in patients with HLA-DR+ KTCs. All psoriasis patients with arthritis received nonsteroidal antiinflammatory drug therapy; 14 received additional therapy directed primarily to the cutaneous manifestations of psoriasis. Nine of these noted arthritis improvement with concurrent skin response; however, in 5 patients, arthritis activity increased, despite improvement of the cutaneous disease. Two other patients, treated with methotrexate, also had concurrent skin and joint improvement. These data suggest that psoriasis patients with HLA-DR+ KTCs are at increased risk for the development of associated arthritis.

RNA, DNA, and cell surface characteristics of lesional and nonlesional psoriatic skin

We have measured the RNA and DNA content and examined cell surface characteristics of human epidermal cells derived from normal skin, and lesional and nonlesional areas of psoriatic skin prior to and following treatment on a modified Goeckerman protocol. Our results show that cells from active psoriatic lesions contain greater numbers of basal keratinocytes when compared with either nonlesional skin from the same patients or skin from healthy volunteers and individuals with other inflammatory skin lesions. Follow-up measurements 2-3 weeks after the initiation of therapy showed that the numbers of basal keratinocytes in resolving psoriatic lesions had decreased and approached normal levels. Multiparameter RNA/DNA flow cytometric analysis on parallel samples from the same psoriasis patients revealed an increased growth fraction and proportion of cycling cells in both the nonlesional and lesional skin compared with controls. Furthermore, the cellular RNA content was elevated in lesional psoriatic skin when compared with either nonlesional or normal skin. Flow cytometric examination of nonlesional and lesional epidermal cells obtained 2-3 weeks after the commencement of therapy revealed that the growth fraction and mean RNA content of the keratinocytes from resolving psoriatic plaques decreased in response to therapy. In contrast, the proportion of keratinocytes within the S + G2 + M phases of the cell cycle remained elevated. These data indicate that "uninvolved" psoriatic skin exhibits characteristics more closely resembling lesional psoriatic skin than normal skin. The results further suggest that quantitation of cellular RNA content and basal cell number might be sensitive indicators of early treatment response in psoriasis.

Expression of HLA-DR molecules by keratinocytes, and presence of Langerhans cells in the dermal infiltrate of active psoriatic plaques

Immunoperoxidase staining of skin sections and immunofluorescence analysis of keratinocyte suspensions obtained from suction blisters of psoriatic plaques were performed using an mAb, Josh 524.4.1, and Fab'2 fragments of a rabbit antiserum, both of which are directed against nonpolymorphic determinants of HLA-DR molecules. HLA-DR+ keratinocytes were present in plaques, but not normal-appearing skin, from a significant portion of patients with active psoriasis. Double-labelling immunofluorescence experiments with either the monoclonal or polyclonal anti-HLA-DR antibody, in conjunction with the mAb OKT6, which identifies DR+ Langerhans cells, demonstrated that HLA-DR molecules were present on OKT6- keratinocytes. The dermal infiltrate of psoriatic plaques contained T cells expressing the activation antigens, IL-2 receptor (Tac) and HLA-DR, as well as macrophages and OKT6+ cells. There was little difference in the characteristics of the dermal infiltrate between the lesions with or without HLA-DR+ keratinocytes. OKT6+ presumptive Langerhans cells were also found in the dermal infiltrates of patients with lichen planus, contact dermatitis, spongiotic dermatitis, erythema multiforme, basal and squamous cell carcinoma. Studies of keratinocyte suspensions showed that 7-84% of keratinocytes were HLA-DR+. Flow cytometry experiments showed that keratinocytes at all stages of differentiation were HLA-DR+. However, the stem cell-enriched population contained the highest proportion of HLA-DR+ cells. HLA-DR expression by keratinocytes correlated with disease activity. The expression was reversible with successful medical therapy. HLA-DR+ keratinocytes may activate T cells directly or may present an as yet unknown antigen to T cells. These studies provide further support for the hypothesis that immunological mechanisms play an important role in the pathogenesis of psoriasis.

Paromomycin therapy of endemic amebiasis in homosexual men

A prospective evaluation was made of the therapeutic efficacy of paromomycin, an orally administered, nonabsorbable aminoglycoside, in 114 homosexual men with mild-to-moderate (nondysenteric) intestinal amebiasis. All patients received 25-35 mg/kg daily in three divided doses for seven days. Of the 80 patients with gastrointestinal complaints at the onset of therapy, 55 (80%) of 69 were asymptomatic within four to six weeks after completion of treatment; 11 patients were lost to follow-up. Paromomycin produced long-term eradication of intestinal Entameba histolytica infection in 92% of all men evaluated. The rate of microbiologic cure among patients with symptoms at the onset of therapy was comparable to that among asymptomatic individuals. Paromomycin was well tolerated, with mild diarrhea during therapy the only frequent adverse effect (67% of patients). Thus, paromomycin is an effective alternative to conventional multi-drug therapy for intestinal amebiasis, and it has the advantages of low toxicity, brief duration of therapy, and a high rate of patient compliance.

Human keratinocyte culture. Identification and staging of epidermal cell subpopulations

Stratification of human epidermal cells into multilayered sheets composed of basal and suprabasal layers (resembling the stratum germinativum and stratum spinosum of the epidermis) was studied in a dermal component-free culture system. Although no stratum corneum developed in vitro, this culture system provided a method to study early events in human keratinocyte differentiation. Multiparameter flow cytometric analysis of acridine orange-stained epidermal cells from these cultures revealed three distinct subpopulations differing in cell size, RNA content, and cell cycle kinetics. The first subpopulation was composed of small basal keratinocytes with low RNA content and a long generation time. The second subpopulation consisted of larger keratinocytes, having higher RNA content and a significantly shorter generation time. Finally, the third subpopulation contained the largest cells, which did not divide, and represent the more terminally differentiated keratinocytes. This in vitro approach provides discriminating cytochemical parameters by which the maturity of the epidermal cell sheets can be assessed prior to grafting onto human burn patients.

Purification and in vitro growth of human epidermal basal keratinocytes using a monoclonal antibody

We have made a new monoclonal antibody, EL-2, and used it with an immunorosetting procedure combined with Ficoll-Hypaque gradient centrifugation to purify and culture basal keratinocytes. Immunofluorescence of cell suspensions and immunoperoxidase staining of tissue sections demonstrate that EL-2 reacts with malignant cell lines, activated lymphocytes and monocytes, and basal keratinocytes. Sequential immunoprecipitation studies demonstrate that monoclonal antibodies EL-2 and 4F2 detect the same membrane protein. However, we have extended previous studies by making the new observation that both EL-2 and 4F2 react with cultured melanocytes. Basal keratinocytes were purified from single-cell epidermal suspensions by incubation with EL-2 followed by rosetting with rabbit antimouse IgG antibodies covalently linked to bovine red blood cells. Rosetting (basal) keratinocytes were separated from EL-2 negative cells by Ficoll gradient centrifugation. We obtained basal keratinocyte populations of greater than 90% purity as assessed by reactivity with EL-2 and another basal keratinocyte-specific monoclonal antibody, HCl. Langerhans cell, fibroblast, and melanocyte contamination was negligible. Cultures of basal keratinocytes were enriched in EL-2-reactive cells throughout the entire 19 days of culture studied. EL-2 is being used to characterize disorders of keratinocyte proliferation; EL-2 reacted with both squamous and basal cell carcinomas. EL-2 stained only the basal layer of lesional skin from patients with psoriasis, pityriasis rubra pilaris, and Darier's disease. Purification of basal keratinocytes will be important in biochemical and functional studies of normal skin and in establishing long-term keratinocyte lines from normal cells.

Cloned allospecific human helper T cell lines induce an MHC-restricted proliferative response by resting B cells

To analyze helper T (Th) cell-induced B cell proliferation in man, we have cloned allospecific Th cells, grown them as long-term IL 2-dependent T cell lines (TCL), and analyzed their phenotypic and functional properties. The two TCL described in this report, A-7 and A-57, are both composed exclusively of T3+, T4+, T8- T cells blasts. In proliferative assays, with a panel of x-irradiated allogeneic stimulator cells, A-7 was found to proliferate in response to DR3-bearing cells, whereas A-57 responds to DR2-positive stimulators. Both TCL are capable of providing MHC-restricted polyclonal help for allogeneic B cells, as measured in the reverse hemolytic plaque assay. Of greater interest, x-irradiated A-7 and A-57 cells are capable of inducing a proliferative response by allogeneic B cells that is absolutely MHC restricted at the inductive (Th-APC) level. Thus, x-irradiated A-7 cells only trigger proliferation by DR3+ B cells, whereas A-57 cells selectively activate DR2+ B cells. In contrast, after antigen-specific activation, x-irradiated A-7 and A-57 cells can recruit a significant proliferative response by allogeneic B cells bearing "irrelevant" DR antigens. The possibility that Th-induced B cell proliferation may be restricted at the effector (Th-B cell) level was addressed by fractionating B cell populations into "activated" and "resting" subsets by discontinuous Percoll density gradient centrifugation and further purification by employing a monoclonal antibody directed against an antigen expressed on activated B cells (4F2). These studies demonstrate that activated B cells are readily and nonspecifically recruited to proliferate by activated Th cells, whereas optimal proliferative responses by resting B cells require MHC restricted Th-B cell interaction.

Cloned allospecific human helper T cell lines induce an MHC-restricted proliferative response by resting B cells

To analyze helper T (Th) cell-induced B cell proliferation in man, we have cloned allospecific Th cells, grown them as long-term IL 2-dependent T cell lines (TCL), and analyzed their phenotypic and functional properties. The two TCL described in this report, A-7 and A-57, are both composed exclusively of T3+, T4+, T8- T cells blasts. In proliferative assays, with a panel of x-irradiated allogeneic stimulator cells, A-7 was found to proliferate in response to DR3-bearing cells, whereas A-57 responds to DR2-positive stimulators. Both TCL are capable of providing MHC-restricted polyclonal help for allogeneic B cells, as measured in the reverse hemolytic plaque assay. Of greater interest, x-irradiated A-7 and A-57 cells are capable of inducing a proliferative response by allogeneic B cells that is absolutely MHC restricted at the inductive (Th-APC) level. Thus, x-irradiated A-7 cells only trigger proliferation by DR3+ B cells, whereas A-57 cells selectively activate DR2+ B cells. In contrast, after antigen-specific activation, x-irradiated A-7 and A-57 cells can recruit a significant proliferative response by allogeneic B cells bearing "irrelevant" DR antigens. The possibility that Th-induced B cell proliferation may be restricted at the effector (Th-B cell) level was addressed by fractionating B cell populations into "activated" and "resting" subsets by discontinuous Percoll density gradient centrifugation and further purification by employing a monoclonal antibody directed against an antigen expressed on activated B cells (4F2). These studies demonstrate that activated B cells are readily and nonspecifically recruited to proliferate by activated Th cells, whereas optimal proliferative responses by resting B cells require MHC restricted Th-B cell interaction.

A membrane protein preferentially expressed by a subpopulation of immature lymphoid cells, epidermal basal keratinocytes, and other epithelial cells

A murine monoclonal antibody, designated EL-1, was raised by immunization with a human malignant T cell line. It reacted specifically with a membrane antigen expressed on T and B lymphoblastoid cell lines, a subpopulation of normal thymocytes and bone marrow lymphocytes, lymphocytes from a subset of patients with non-B, non-T cell acute lymphoblastic leukemia or T cell acute lymphoblastic leukemia and epithelial stem cells. The latter reactivity was especially striking in the skin, where only basal epidermal keratinocytes and epidermal appendages, including eccrine sweat glands, sebaceous glands and hair follicles, stained positively. A human epidermoid carcinoma cell line was also stained by EL-1. Suprabasilar keratinocytes and acellular keratin did not stain. However, in vitro proliferating fetal lung fibroblasts stained positively. Membrane immunoprecipitation analysis demonstrated that the antigen recognized by antibody EL-1 is a single protein of molecular weight 105 kilodaltons which did not change with exhaustive chemical reduction. Metabolic radiolabeling studies demonstrated that this protein is synthesized by the cell and not merely taken up from the culture medium. This antibody can be useful in studying keratinocyte differentiation in epidermal malignancies and normal skin.

Soluble factors inhibitory for T-cell-dependent immune responses in patients with the acquired immune deficiency syndrome and its prodromes

Supernatants from PBMC obtained from certain patients with AIDS or its prodrome were capable of depressing pokeweed mitogen-driven immunoglobulin production and the proliferative response of T cells to specific antigen. These soluble suppressor factors (SSF) were present in uniquely high concentrations, and were the product of an interaction of T lymphocytes with adherent cells. T-cell independent functions were not modified by soluble suppressor factors. Restoration of immunoglobulin synthesis in SSF-treated cultures was realized by addition of reducing agents such as 2-mercaptoethanol, suggesting inhibitory mechanisms possibly related to that of Con A-induced soluble immune response suppression, and perhaps offering clues to clinically applicable substances capable of modifying such responses. A relationship between SSF-AIDS and a human retrovirus LAV/HTLV III, linked etiologically to AIDS and its prodromes, is suggested by studies of SSF-like substances released by human T-T cell hybridomas derived from LAV+ patients.

Soluble suppressor factors in patients with acquired immune deficiency syndrome and its prodrome. Elaboration in vitro by T lymphocyte-adherent cell interactions

Supernatants from peripheral blood mononuclear cells obtained from certain patients with the acquired immune deficiency syndrome (AIDS) or its prodrome were capable of depressing spontaneous and pokeweed mitogen-driven B lymphocyte differentiation into plasmacytes, and the proliferative responses of T cells to specific antigen. These soluble suppressor factors (SSF) were present in uniquely high concentrations, with significant differences from healthy controls and from patients with various other conditions previously associated with factor-mediated immunosuppression. T cell-independent functions were not modified by SSF. Suppression was not genetically constrained, and did not appear to be mediated by cytotoxicity, prostaglandin, or alpha or gamma interferons. SSF was a product of the interaction of T lymphocytes with adherent cells. T cells or T cell factors from AIDS patients, but not from normal controls, could collaborate with control adherent cells in the formation of SSF. Restoration of DNA synthesis-independent differentiation of B lymphocytes into plasmacytes in SSF-treated cultures was realized by addition of reducing agents, such as 2-mercaptoethanol, on culture initiation. These data suggest inhibitory mechanisms possibly related to that of concanavalin A-induced soluble immune response suppression, and perhaps offer clues to clinically applicable substances which are potentially capable of mitigating such responses.

Poor mixed lymphocyte reaction stimulatory capacity of leukemic B cells of chronic lymphocytic leukemia patients despite the presence of Ia antigens

The human Ia-like antigens, selectively expressed on B lymphocytes, are now recognized to be closely associated with, or identical to, the gene products of the major histocompatibility complex responsible for stimulation in the mixed lymphocyte reaction. The leukemic B lymphocytes of patients with chronic lymphocytic leukemia express these antigens very well. In the present study they were readily detected by several techniques utilizing both allo- and heteroantisera. However, the leukemic B cells from most patients were found to be extremely poor stimulating cells in the mixed lymphocyte reaction. This was particularly apparent when comparisons were made on a B-cell basis with isolated normal B lymphocytes. Leukemic cell death, abnormal kinetics of leukemic cell-mediated stimulation, and serum or cellular suppressor factors do not appear to explain these findings. Studies comparing cells from a leukemic patient with those of her HLA identical sibling and results of mixed lymphocyte reactions between normal and leukemic subjects discordant for D-region-associated Ia antigens ruled out genetic explanations for the differences observed. Experiments with normal peripheral blood mononuclear cells depleted of T cells and monocytes exclude the quantitative deficiency of monocytes which is found in the peripheral blood of most leukemic patients as an explanation. The present results with chronic lymphocytic leukemia cells indicate that the mere expression of the Ia-like antigens by cell populations does not render them effective stimulators. The accumulated evidence obtained indicate that abnormalities, particularly of membrane function and metabolism, known to occur in chronic lymphocytic leukemia lymphocytes may be involved in the poor stimulatory capacity of the leukemic B cells.

Immune function in systemic lupus erythematosus. Impairment of in vitro T-cell proliferation and in vivo antibody response to exogenous antigen

Peripheral blood mononuclear cells from 46 systemic lupus erythematosus (SLE) patients showed reduced ability to proliferate in vitro in response to the soluble antigen, tetanus toxoid, as compared with 96 normal controls. Special studies of 27 untreated SLE patients also revealed significantly decreased blastogenic responses to tetanus toxoid. In both the total and untreated SLE populations, decreased mean tetanus antibody titers also were found as compared with the control population. However, the reduction in antibody titer and blastogenic response was not strictly parallel. A limited immunization program was initiated in low-responding volunteers from the SLE and normal populations. Three out of four SLE patients did not develop a significant blastogenic response despite increases in anti-tetanus titers after immunization, whereas all normals showed significant increases in both blastogenic and antibody responses. The accumulated evidence indicated that the unresponsiveness was the result of a defect in T-cell function. Monocyte reactivity was demonstrated to be normal, and no evidence was found for the presence of suppressor cells, inhibition by immune complexes, or increased prostaglandins to explain the defect.

Ia-bearing T lymphocytes in man. Their identification and role in the generation of allogeneic helper activity

The presence of Ia-like antigens was demonstrated on a small population (2-6%) of highly purified human circulating T lymphocytes by immunofluorescence with a rabbit anti-Ia serum raised against the isolated bimolecular Ia structure. The Ia+ T lymphocytes have no surface or intracellular immunoglobulins. The expansion of this Ia+ T-cell population was encountered in certain patients. Ia antigens were also found on T blasts grown in long-term cultures with conditioned medium generated by phytohemagglutinin-stimulated lymphocytes. In addition, leukemia blasts which stained for Ia antigens and formed E rosettes were identified in the peripheral blood of two leukemic patients. This evidence further supports the existence of Ia-bearing T cells in man. The Ia+ T-lymphocyte population was shown to contain cells responsible for the generation of allogeneic helper activity. Elimination of Ia+ lymphocytes from a purified T-cell population by the anti-Ia antiserum and complement abolished its ability to help an allogeneic B-cell preparation to generate plaque-forming cells against sheep erythrocytes in vitro in the presence of the antigen.

A cross-reaction between beta2-microglobulin and kappa-light chains

Certain antisera to immunoglobulins containing kappa-chains show the presence of antibodies that cross-react with beta2-microglobulin. This was most apparent with an antiserum made to highly purified F(ab) fragments of Fr II gamma-globulin. These cross-reactive antibodies caused positive fluorescence and cytotoxicity reactions with a variety of cell types including T cells. These reactions were completely removed by absorption with highly purified kappa-chains but not with lambda-chains or lambda immunoglobulins. beta2-microglobulin preparations also absorbed or inhibited the special cellular reactivities. Evidence was obtained that HLA-bound beta2-microglobulin was more efficient in this respect. The possibility is discussed that similar cross-reactive antibodies may have been involved in some previous studies of inhibition of T cell function by immunoglobulin antisera.

A Cross-Reaction between β2-Microglobulin and κ-Light Chains

Certain antisera to immunoglobulins containing κ-chains show the presence of antibodies that cross-react with β2-microglobulin. This was most apparent with an antiserum made to highly purified F(ab) fragments of Fr II γ-globulin. These cross-reactive antibodies caused positive fluorescence and cytotoxicity reactions with a variety of cell types including T cells. These reactions were completely removed by absorption with highly purified κ-chains but not with λ-chains or λ immunoglobulins. β2-microglobulin preparations also absorbed or inhibited the special cellular reactivities. Evidence was obtained that HLA-bound β2-microglobulin was more efficient in this respect. The possibility is discussed that similar cross-reactive antibodies may have been involved in some previous studies of inhibition of T cell function by immunoglobulin antisera.

An unusual kappa immunoglobulin antigen present on the membrane of T and B lymphocytes

Several K immunoglobulin antisera out of a large number studied showed the unique property of reacting with a membrane structure present on all T and B lymphocytes examined. This antigen was detected on lymphocytes by indirect fluorescence, direct fluorescence, and by cytotoxic analysis. Absorption of the antiserum by all K myeloma proteins, K Bence-Jones proteins, and kappa light chains removed the activity; L proteins had no effect. The possibility that the cross-reacting membrane antigen is part of the HL-A system was discussed.

Quantitative determination of allotypic and idiotypic markers with antisera coupled to N-hydroxysuccinimide-activated sepharose

N-hydroxysuccinimide activated Sepharose beads (HAS) were used to immobilize allotypic and idiotypic antisera for use in radioimmunoassays. These HAS antisera were compared to antisera solidified with ethylchloroformate (ECF) with respect to their reactivity, specificity, and ability to detect subspecificities of the group a allotypes. The HAS antisera rated favorably in all comparisons with ECF antisera and are far superior with respect to ease of preparation and retention of antibody activity.