Influence of 1,25-(OH)2 vitamin D3 and gamma interferon on the phenotype of human peripheral blood monocyte-derived macrophages

The effects of 1,25-dihydroxy vitamin D3 and gamma interferon on the phenotypic changes associated with monocyte maturation in vitro were investigated. Human monocytes separated from peripheral blood mononuclear cell populations by adherence to plastic were cultured for 7 days on glass. Immunocytological analysis was performed on monolayers fixed at various times by using monoclonal antibodies specific for mature macrophages (RFD7), interdigitating (dendritic) cells (RFD1), and class II major histocompatibility complex antigen (RFDR1). Without any addition to the culture medium, proportions of these monocytes (normally RFD1 and RFD7 negative) developed either RFD1 positivity (23%) or RFD7 positivity (49%) over 7 days of culturing. The addition of gamma interferon to these cultures markedly reduced the proportion of RFD7-positive cells (less than 10%) but increased the proportion of RFD1-positive cells (40 to 60%). In contrast, 1,25-dihydroxy vitamin D3 reduced the expression of both RFD1 and RFD7. Both of these effects were dose dependent and required at least 3 days of contact with the cells. The possibility that RFD1- and RFD7-positive cells represent functionally distinct subsets makes these effects of significance in our understanding of the role of these mediators in controlling the immunocompetence of nonlymphoid accessory cell populations and in macrophage-associated antimicrobial activity.     

Effect of mycobacteria on sensitivity to the cytotoxic effects of tumor necrosis factor

Unlike Mycobacterium leprae, Mycobacterium tuberculosis is not found inside cells other than macrophages and polymorphonuclear cells in vivo, yet previous work has revealed that in vitro it readily enters all cell lines tested. Moreover, these cells are not killed by the intracellular mycobacteria. We report here that when fibroblasts take up live (but not killed) M. tuberculosis H37Rv, they develop greatly increased sensitivity to the toxic effects of tumor necrosis factor (TNF) whether the cell line is inherently sensitive to TNF or not. Ultrasonically disrupted M. tuberculosis also has this property. The increased sensitivity is seen in the absence of metabolic inhibitors, although addition of emetine, an inhibitor of protein synthesis, causes the effect to manifest itself earlier and at a lower concentration of TNF. In contrast, infection with Mycobacterium bovis bacillus Calmette-Guérin induces little or no increased sensitivity to TNF, whereas Mycobacterium avium and M. tuberculosis H37Ra have intermediate sensitivities. We discuss the possibility that virulent tuberculosis strains produce a factor which distorts the normal protective function of TNF, rendering it toxic to host tissues and leading to the classical immunopathology of tuberculous lesions.     

Vitamin D3, gamma interferon, and control of proliferation of Mycobacterium tuberculosis by human monocytes.

Previous studies have shown that recombinant interferon gamma (IFN-gamma), crude T cell supernatants, or appropriate T-cell lines can cause total inhibition of the growth of M. tuberculosis inside murine peritoneal macrophages. In similar experiments with human monocytes much smaller effects are seen. This could be due to the relative immaturity of these cells. Because dihydroxy vitamin D3 (1,25-(OH)2 D3) can cause phenotypic differentiation of immature leukemic lines into macrophage-like cells, we have explored the possibility that exposure to cholecalciferol metabolites in vitro might increase the ability of monocytes to control proliferation of M. tuberculosis, or cause monocytes to mature into cells able to respond appropriately to IFN-gamma. Incubation of monocytes with three cholecalciferol metabolites induced anti-tuberculosis activity to an extent that correlated with their binding affinities to the intracellular receptor protein for the derivatives. 1,25-(OH)2 D3 also primed monocytes for phorbol myristate acetate-triggered reduction of nitroblue tetrazolium. The effects were additive rather than synergistic with those of IFN-gamma. Monocytes incubated with IFN-gamma developed 25-OH D3 1-hydroxylase activity, detected by conversion of tritiated 25-(OH) D3 to a more polar metabolite which coeluted with 1,25-(OH)2 D3 on straight and reverse-phase HPLC. The latter is a more active form in vivo. These findings help to explain claims for the efficacy of vitamin D in the treatment of some forms of tuberculosis, and also the occasional finding of raised serum calcium, and disturbed vitamin D metabolism in these patients.     

The interaction of Tamm-Horsfall protein with the extracellular matrix.

Tamm-Horsfall protein (THP) is the major glycoprotein component of urine, yet its biological role remains obscure. Recent reports have suggested that a concanavalin A (Con A)-binding fraction of THP from pregnancy urine can bind the cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1). In order to investigate this claim in relation to THP from normal adult urine we raised monoclonal antibodies to THP and sought THP/TNF-alpha interactions in three separate assay systems. We found no evidence that THP binds to TNF-alpha under physiological conditions, but we observed that it exerts a weak, probably not physiologically relevant, but reproducible inhibitory effect on the toxicity of TNF-alpha for monolayers of L929 cells, even when the cells are pretreated with the THP, and washed before addition of the cytokine. Since our preparations of THP do not interact directly with TNF-alpha we postulated an interaction with the cells themselves, or with their extracellular matrix. The THP was found by ELISA, immunoblotting and immunohistology, to bind to as yet unidentified components of the extracellular matrix in a manner dependent on cations, pH and carbohydrates. These data, considered in the light of the published amino acid sequence and biochemical properties, suggest that THP is a member of a structural glycoprotein family known to modulate cell adhesion.     

Differing role of dendritic cells and macrophages in the induction of delayed-type hypersensitivity responses to PPD.

In order to study the antigen-presenting cell (APC) requirements for the priming of delayed-type hypersensitivity (DTH), murine spleen cells were fractionated on bovine serum albumin gradients, pulsed in vitro with tuberculin, and then injected subcutaneously into normal mice. The other footpad was challenged with tuberculin between 24 hr and 7 days later and swelling was measured 2 hr and 18-24 hr after challenge. Optimum priming for 2-hr and 24-hr responses at 7 days was achieved by an injection of 5 X 10(5) tuberculin-pulsed intermediate-density Fc + ve cells. Time-course studies revealed that the 2-hr component could be elicited as early as 24 hr after injection of pulsed APC, while the 24-hr component became significant at 3 days. Elimination of T cells or B cells did not affect the response. Injection of pulsed APC into allogeneic mice primed the 2-hr but not the 24-hr component. Neither pulsed high-density cells (mostly T cells) nor pulsed dendritic cells (DC) primed mice for these responses. Failure to elicit DTH after injection of tuberculin-pulsed DC was due to their failure to prime the 2-hr component, which other authors have shown to be a prerequisite for the appearance of the later components. That DC did prime the MHC-restricted 24-hr component was demonstrated by protocols involving the use of both macrophages and DC as APC.     

Maintained pregnancy levels of oestrogen afford complete protection from post-partum exacerbation of collagen-induced arthritis.

Pregnancy is known to influence the course of rheumatoid arthritis (RA) in women, as well as type II collagen-induced arthritis (CIA) in DBA/1 mice. A characteristic feature is the remission during gestation and the exacerbation of the diseases during the post-partum period. In the case of CIA in DBA 1 mice, two hormonal changes have been assumed to be critical for the induction of the post-partum flare: (i) the fall in steroid hormone levels from those present during pregnancy; and (ii) surges of prolactin (PRL) release at and after delivery. Our results show that treatment with oestradiol during a short period immediately after parturition protects the mouse from a post-partum flare of the disease, and that treatment with bromocriptine, a drug known to inhibit the endogenous PRL release, has a significant though less marked effect. Studies of lactating (i.e. animals with physiological stimulation of endogenous PRL release) and non-lactating arthritic mice revealed no clear-cut differences, indicating that PRL is of minor importance for the induction of the post-partum flare. Some steroids other than oestradiol, which may be implicated in the exacerbation of arthritis, namely progesterone and hydrocortisone, had no clinical effect. Analyses of agalactosyl IgG levels in mice with CIA, and anti-collagen II antibodies in sera collected at the end of the experiments revealed no significant differences between the oestradiol and the control groups. The successful oestradiol treatment of the mice indicates that the drop in endogenous oestradiol levels prior to delivery ends the oestrogen-mediated protection against arthritis during pregnancy.     

Induction of delayed-type hypersensitivity responses to PPD: dendritic cells in synergy with 5-hydroxytryptamine can substitute for macrophages.

We describe the use of 5-hydroxytryptamine (5HT) as an adjuvant in the induction of the delayed-type hypersensitivity (DTH) response to purified protein derivative (PPD). Based upon our previous studies with antigen-pulsed macrophages (M phi), we have shown that both the Day 2 early (2 hr) reaction and the Day 3 (24 hr) reaction are augmented if 5HT is incorporated into the priming injection. Furthermore, we have confirmed that in contrast to M phi, antigen-pulsed dendritic cells (DC) fail to prime the early (2 hr) component of DTH. However, DC do prime the early response if injected along with 5HT. A peripheral 5HT antagonist, ICS 205-930, inhibits both the M phi-mediated and the 5HT/DC-primed reactions. These findings support the hypothesis that DTH reactions require a cascade of both inflammatory and immunological signals, and that in mice vascular permeability mediated via 5HT is important in the early phase of the reaction.     

An association between Gc (vitamin D-binding protein) alleles and susceptibility to rheumatic fever.

Rheumatic fever is associated with exaggerated activity of B cells with massive production of antibody to the Group A streptococcus. Gc (vitamin D-binding protein) is constitutively expressed on B-cell membranes in association with membrane immunoglobulin, and could be involved in cell activation. We therefore looked for associations between the three major Gc alleles and susceptibility to rheumatic fever in a homogeneous Arab population. Patients with tuberculosis or rheumatoid arthritis and control donors, were studied in parallel. Allele frequencies in the controls, rheumatoid and tuberculosis patients were identical to those found in a previous study of normal Arab donors. However, there was a striking association between Gc2 and rheumatic fever. This allele was twice as common in these patients as in controls (p = 0.0024), and was present in 56.4% of all rheumatic fever patients.