Thomas R. Cupps

Corticosteroid-mediated immunoregulation in man.

Glucocorticoids have profound and complex effects on the human immune response. However, the precise mechanisms of the corticosteroid-induced immunoregulation in man have not been precisely defined. Intracytoplasmic corticosteroid-specific receptors appear to be an important common pathway for steroid-induced changes, but variations of receptor parameters do not account for the multifaceted effects on the immune system. Human circulating mononuclear cells redistribute out of the intravascular compartment following treatment with corticosteroids. Although certain components at this redistribution phenomenon have been well-characterized, the importance of this compartmental cellular shift with respect to the mechanisms of corticosteroid-induced immunoregulation are less well-defined. Recent observations that activated lymphocytes may be sensitive to the lytic effects of glucocorticoids suggest that under certain situations the elimination of selected subsets of cells may be a relevant mechanism of corticosteroid-mediated immunoregulation in man. Corticosteroid-mediated effects on monocyte function may be an important mechanism of drug-induced immunoregulation in monocyte-dependent responses. In some experimental conditions, corticosteroids inhibit Interleukin 1 production by monocytes. The immunoregulatory effects of corticosteroids on lymphocyte immune responses are complex. In vitro corticosteroids appear to selectively affect early immunoregulatory events as opposed to altering an established response. Multiple sites of steroid-induced modulations of human B cell responses have been defined.

Glucocorticoid Therapy for Immune-Mediated Diseases: Basic and Clinical Correlates

Dr. Dimitrios T. Boumpas (Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases [NIDDK], National Institutes of Health [NIH], Bethesda, Maryland): Since 1949, when Hench and colleagues first introduced cortisone for the treatment of rheumatoid arthritis, glucocorticoids have revolutionized the treatment of immunologically mediated diseases. Although substantial complications associated with glucocorticoids have tempered enthusiasm for their use, they have remained the cornerstone of therapy for virtually all immunologically mediated diseases. In recent years, an explosion of new information has occurred relevant to both basic and clinical aspects of glucocorticoid therapy. We describe the molecular mechanisms, sites of action, and effects of glucocorticoids on various cells involved in inflammatory and immunologically mediated reactions. Treatment principles are also provided with examples of specific glucocorticoid regimens in prototypical conditions. We also review selective complications of glucocorticoid therapy and discuss recent information about their pathogenesis and management. Mechanisms of Action Dr. George P. Chrousos (Chief, Pediatric Endocrinology Section, Developmental Endocrinology Branch, National Institute of Child Health and Human Development, NIH, Bethesda, Maryland): Glucocorticoids exert most of their effects through specific, ubiquitously distributed intracellular receptors [1]. The classic model of glucocorticoid action was described more than two decades ago and is briefly updated here (Figure 1, panel A). Glucocorticoids circulate in blood, is either in the free form or in association with cortisol-binding globulin. The free form of the steroid can readily diffuse through the plasma membrane and can bind with high affinity to cytoplasmic glucocorticoid receptors (the role of receptors primarily residing in the nucleus is controversial). The formation of the ligand-receptor complex is followed by its activation (that is, translocation into the nucleus and binding to what are called acceptor sites). The bound complex modulates transcription of specific genes that encode proteins responsible for the action of glucocorticoids. Figure 1. Mechanisms of glucocorticoid action. Panel A. Panel B. Glucocorticoid Receptors In 1985, the complementary DNA of the human glucocorticoid receptor was cloned [2]; it contains three main functional domains Figure 1, panel B): first, the DNA-binding domain in the center of the molecule that recognizes specific sequences of the DNA called hormone-responsive elements; second, the ligand-binding domain in the carboxyl terminal region that interacts with the specific steroid; and third, the immunogenic domain in the amino terminal region. The nonactivated glucocorticoid receptor resides in the cytosol in the form of a hetero-oligomer with other highly conserved proteins [3]. This molecular complex comprises receptor, heat-shock proteins, and immunophilin (Appendix Table 1) [4]. The binding of the receptor to the heat-shock protein 90 facilitates its interaction with the ligand [5]. When the ligand binds, the receptor dissociates from the rest of the hetero-oligomer and translocates into the nucleus. Before or after the translocation, the receptor forms homodimers through sequences present in the DNA and ligand-binding domains [6]. Appendix Table 1. Glossary of Genetic Terms Gene Regulation After specific interaction with pore-associated proteins, the hormone-receptor complexes enter the nucleus through the nuclear pores [7]. The interaction is facilitated by two nuclear localization sequences in the receptor, both in the ligand-binding domain. Inside the nucleus, the hormone-receptor complexes bind to specific glucocorticoid responsive elements within DNA [8]. The complexes modulate the transcription rates of the corresponding glucocorticoid-responsive genes [9], apparently by stabilizing the initiation complex, composed of RNA polymerase II and its ancillary factors A through F. The hormone-receptor complex may interact directly with factor IIB [10], but it also interacts with other nuclear proteins to produce the conditions necessary for effective transcription [11]. These proteins may be able to relax the DNA away from the nucleosome and thus make it easier for the polymerase to exert its effects. In addition, glucocorticoid receptors may interact with DNA-binding proteins that are associated with different regulatory elements of the DNA [12, 13]. At least two such proteins have been described: One is the glucocorticoid modulatory element-binding protein and the other is the CACCC-box-binding protein. Both of these transcription factors potentiate the modulatory effects of glucocorticoids after transcription of specific genes. Transcription appears to be important in the regulation of genes involved in growth and inflammation. Glucocorticoid response elements can act both positively and negatively on transcription, depending on the gene on which the complex acts [14, 15]. One major way by which glucocorticoids exert down-modulatory effects on transcription is through noncovalent interaction of the activated hormone-receptor complex with the c-Jun/c-Fos heterodimer [16-18], which binds to the activator protein (AP)-1 site of genes of several growth factors and cytokines. The glucocorticoid-receptor complex prevents the c-Jun/c-Fos heterodimer from stimulating the transcription of these genes. Another mechanism by which glucocorticoids may suppress gene transcription is by an interaction between the hormone-receptor complex and glucocorticoid response elements that are in close proximity to responsive elements for other transcription factors [19]. Thus, the promoter region of the glycoprotein hormone- subunit, which is stimulated by cyclic AMP through the cyclic AMP-responsive element, contains a glucocorticoid response element in close proximity, so that when the receptor dimer binds to its own element, it hinders the cyclic AMP-binding protein from exerting its stimulatory effect on that gene. Post-Transcriptional Effects In addition to modulating transcription, glucocorticoids also have effects on later cellular events, including RNA translation, protein synthesis, and secretion. They can alter the stability of specific messenger RNAs of several cytokines and other proteins, thereby altering the intracellular steady-state levels of these molecules [20, 21]. This may occur through modulation of transcription of still unknown proteins that bind RNA and alter its translation and degradation rates. Also, glucocorticoids influence the secretion rates of specific proteins through mechanisms that have not yet been defined. Finally, the receptor itself has guanylate cyclase activity, and glucocorticoids can rapidly alter the electrical potential of some cells [22, 23]. Anti-inflammatory and Immunosuppressive Effects Dr. Dimitrios T. Boumpas: Although the cause and pathogenesis of many immunologically mediated diseases are not completely understood, it is known that the localization of leukocytes at sites of inflammation, their subsequent activation, and the generation of secretory products contribute to tissue damage, as shown in Figures 2 and 3 [24-26]. Glucocorticoids inhibit the access of leukocytes to inflammatory sites, interfere with their function and the function of fibroblasts and endothelial cells at those sites, and suppress the production and the effects of humoral factors. In general, leukocyte traffic is more susceptible to alteration by glucocorticoids than is cellular function; in turn, cellular immunity is more susceptible than humoral immunity to these agents. Figure 2. Models of the pathogenesis of inflammation and immune injury. Panel A. Panel B. Figure 3. Cellular adhesion molecules. Even though the effects of glucocorticoids on the different types of inflammatory cells will be discussed separately, each cell type is actually involved in complex interactions with other cells. Glucocorticoids affect many, if not all, the cells and tissues of the body, thus provoking a wide range of changes that involve several cell types concurrently. Effects on Nonlymphoid Inflammatory Cells Dr. Ronald L. Wilder (Chief, Inflammatory Joint Diseases Section, Arthritis and Rheumatism Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, NIH, Bethesda, Maryland): Glucocorticoids are among the most potent anti-inflammatory agents available in clinical medicine. Pharmacologic doses of glucocorticoids dramatically inhibit exudation of plasma and accumulation of leukocytes at sites of inflammation. Several factors influence the magnitude of these effects, including the dose and route of administration of the glucocorticoids used, as well as the type and differentiation state of the target cell population [27]. Several host variables also modify the anti-inflammatory response to glucocorticoids. For example, some persons (those with active systemic lupus erythematosus) appear to have an accelerated rate of glucocorticoid catabolism [28]. Various levels of target tissue resistance may exist in some patients with systemic lupus erythematosus and rheumatoid arthritis [29]. These factors, alone or in combination, may explain the observation that different patients and diseases have variable therapeutic responses to glucocorticoids [30, 31]. Macrophages Glucocorticoids antagonize macrophage differentiation and inhibit many of their functions [27]. These agents 1) depress myelopoiesis and inhibit expression of class II major histocompatibility complex antigens induced by interferon-; 2) block the release of numerous cytokines, such as interleukin-1, interleukin-6, and tumor necrosis factor-; 3) depress production and release of proinflammatory prostaglandins and leukotrienes; and 4) depress tumoricidal and microbicidal activities of activated macrophages. Neutrophils The major effect of glucocorticoids on neutrophil

Isolated angiitis of the central nervous system: Prospective diagnostic and therapeutic experience

Isolated angiitis of the central nervous system is an uncommon clinicopathologic entity characterized by vasculitis restricted to the vessels of the central nervous system without other apparent systemic vasculitis. Experience with the diagnosis, treatment, and follow-up evaluation in four patients with this disease is presented. Early manifestations of disease include severe headaches, altered mental function, and focal neurologic deficits. The pattern of progression from headaches and altered mental status to multifocal neurologic deficits is particularly suggestive of the diagnosis of vasculitis of the central nervous system. Systemic symptoms such as fever, myalgia, arthralgia, and arthritis, which occur frequently in other vasculitic syndromes, are generally not present in patients with isolated angiitis of the central nervous system. No single laboratory study can firmly establish or completely exclude the diagnosis; consequently, tissue diagnosis with biopsy of the brain parenchyma and leptomeninges may be required. In two patients, recurrent disease developed despite treatment with corticosteroids alone. Sustained clinical remission was induced in all four patients with a regimen of daily cyclophosphamide and alternate-day prednisone therapy. Cyclophosphamide and alternate-day prednisone therapy are considered the treatment of choice in severe, progressive, or corticosteroid-resistant isolated angiitis of the central nervous system.

Immunoglobulin replacement therapy by slow subcutaneous infusion

Excerpt Alcohol fractionated immune serum globulin and fresh frozen plasma are the only generally available preparations used for replacement therapy in patients with antibody deficiency syndromes....

Hydrocortisone-mediated inhibition of monocyte antigen presentation: Dissociation of inhibitory effect and expression of DR antigens

The suppressive effects of hydrocortisone (HC) on the human immune system are well known. The mediation of the immunosuppressive effects of HC on lymphocyte responses via inhibition of monocyte function has been examined by monocyte-dependent, antigen-induced lymphocyte proliferation. Monocytes that were first treated with HC and then washed were unaffected in their subsequent ability to present antigen. However, there was a dramatic inhibition of lymphocyte proliferative responses if HC was present while monocytes were pulsed with antigen. This was directly related to the dose of HC present. HC-mediated inhibition of monocyte antigen presentation could not be overcome by the addition of interleukin-1 (IL-1) to cultures, and thus inhibition of monocyte IL-1 secretion cannot totally account for the inhibition of monocyte antigen presentation. Although HC inhibits monocyte antigen presentation, HC increases the expression of HLA-DR antigens on monocytes. Other monocyte stimulants, including lipopolysaccharide (LPS), lymphokine, and gamma interferon, were examined for their effect on monocyte DR expression and their effect on monocyte antigen presentation. No correlation was found between the ability to increase monocyte DR antigen expression and the effect on antigen presentation. While HC, lymphokine, and gamma interferon all increased the expression of DR antigens on monocytes, HC, LPS, and lymphokine, but not gamma interferon, inhibited monocyte antigen presentation. Although HC can exert profound immunosuppressive effects via monocytes, it is not the only mechanism of inhibition. HC added to cultures after monocytes had been pulsed with antigen was also inhibitory.

Cyclophosphamide: To pulse or not to pulse?

(lthough daily low-dose (2 mg/kg) oral cyclophosphamide (CP) is effective in the treatment of corticosteroid-resistant vasculitic diseases [l-3], this regimen has a low therapeutic/toxic profile. Major toxicities associated with daily CP administration include neoplasm (acute myelogenous leukemia and bladder cancer), hemorrhagic cystitis, bladder fibrosis, pulmonary fibrosis, bone marrow suppression, ovarian failure, and infection. In an attempt to decrease the morbidity associated with daily CP administration, protocols utilizing intermittent treatment with larger doses of the drug have been developed. Balow, Austin, and colleagues [4-61 have demonstrated that intermittent highdose (1 g/m2) intravenous CP (pulse CP) is as effective as daily low-dose CP in the treatment of systemic lupus erythematosus (SLE) with nephritis. The major advantage of the pulse CP protocols is less long-term drug-related toxicity. When compared with a low-dose daily protocol, pulse CP is associated with a lower incidence of cancer, bladder toxicity, and chronic bone marrow suppression. The use of pulse CP represents a major improvement in the treatment of lupus nephritis with sustained efficacy and decreased toxicity. Based on this successful experience in lupus nephritis, there is a tendency to assume that pulse CP will have comparable efficacy to long-term low-dose daily CP in the treatment of other cytotoxic-responsive diseases. This unwarranted conclusion could lead to the premature use of pulse CP in other CP-responsive diseases, including the systemic vasculitides, prior to the completion of appropriate clinical studies. The report by Hoffman et al [7] raises significant questions about the efficacy of pulse CP in the treatment of patients with Wegener’s granulomatosis. Hoffman et al [7] report results of pulse CP treatment of 14 patients with Wegener’s granulomatosis. The study population is heterogenous and includes

Successful treatment with acyclovir of an immunodeficient patient infected simultaneously with multiple herpesviruses

A patient with recurrent simultaneous chronic infections, including cytomegalovirus pneumonia, disseminated zoster and perineal herpes simplex infection, whose immune responses were deficient (immunodeficient), is presented. Following treatment with acyclovir (19-(2-hydroxyethoxymethyl)guanine), this patient had a rapid remission of these viral infections. The patients clinical improvement is remarkable considering the duration of the viral infections and the continued immune deficiency. Acyclovir appears to act by a highly selective activation by and inhibition of viral enzymes. Prospective trials of this agent in immunosuppressed patients with herpes virus infections seem warranted.

Wegener's Granulomatosis

Wegeners granulomatosis is characterized by a necrotizing granulomatous vasculitis which can be found in both the upper and lower respiratory tracts and with either focal or proliferative glomerulonephritis. However, any organ system can be affected by the disease. Over the past 17 years, 47 patients with histologically proven Wegeners granulomatosis have been treated at the National Institute of Allergy and Infectious Disease. Since 1972, patients with head and neck manifestations have been managed in collaboration with the Department of Otolaryngology, National Naval Medical Center. Experiences with these patients have shown that all have had some degree of respiratory tract involvement, with 42/47 having disease in the nose or paranasal sinuses. An effective therapeutic regimen is possible with immunosuppressants (particularly cyclophosphamide) and locally supportive measures. As a result of such therapy, more than 80% of the patients treated have experienced long-term remissions. The clinical implications of this therapy are discussed, and a protocol for patient management presented.

Increased expression of HLA-DR antigens in hydrocortisone-treated monocytes

Human peripheral blood monocytes incubated overnight with hydrocortisone had an increased expression of HLA-DR antigens. This change was noted as an increased proportion of DR-positive staining monocytes at greater fluorescence intensities as determined on a fluorescence-activated cell sorter. Hydrocortisone treatment of monocytes did not alter the expression of another Ia antigen on monocytes, HLA-DS. Neither did hydrocortisone treatment alter the expression of either Mac 120 antigen or monocyte .2 antigen on monocytes. Thus, the effect of hydrocortisone on monocyte DR antigens may be somewhat selective. Hydrocortisone also caused an increase in monocyte cell size after 3 to 4 days as compared to untreated controls.

Corticosteroid-induced modulation of immunoglobulin secretion by human B lymphocytes: potentiation of background mitogenic signals.

The modulation of immunoglobulin (Ig) secretion of human peripheral blood mononuclear cells by in vitro hydrocortisone (HC) was evaluated. A marked enhancement of Ig secretion was observed in unstimulated cultures in the presence of HC as compared to cultures without HC. The augmented response was not due to a direct induction of Ig secretion by HC, but resulted from an enhancement or unveiling of the background mitogenic signal provided by the supplemental serum used in culture. HC-induced augmentation of Ig secretion was only seen in unstimulated cultures performed in fetal calf serum (FCS) which is known to possess mitogenic properties. In contrast, HC had no significant effect on Ig secretion of cultures performed in human serum, which provides little or no background mitogenic signal. On the other hand, no enhancement of Ig secretion by HC was seen in cultures maximally stimulated with pokeweed mitogen regardless of whether FCS or human A serum was used. The mechanisms of this modulation of Ig secretion are unclear at present and may include a synergy between corticosteroids and background mitogenic signals (such as FCS) indirectly triggering B cells and/or the dampening of a negative immunoregulatory effect of an accessory cell.