Growth hormone activation of human monocytes for superoxide production but not tumor necrosis factor production, cell adherence, or action against Mycobacterium tuberculosis

Growth hormone remodels the 3D-structure of the mitochondria of inflammatory macrophages and promotes metabolic reprogramming

Introduction

Macrophages are a heterogeneous population of innate immune cells that support tissue homeostasis through their involvement in tissue development and repair, and pathogen defense. Emerging data reveal that metabolism may control macrophage polarization and function and, conversely, phenotypic polarization may drive metabolic reprogramming.

Methods

Here we use biochemical analysis, correlative cryogenic fluorescence microscopy and cryo-focused ion-beam scanning electron microscopy.

Results

We demonstrate that growth hormone (GH) reprograms inflammatory GM-CSF-primed monocyte-derived macrophages (GM-MØ) by functioning as a metabolic modulator. We found that exogenous treatment of GM-MØ with recombinant human GH reduced glycolysis and lactate production to levels similar to those found in anti-inflammatory M-MØ. Moreover, GH treatment of GM-MØ augmented mitochondrial volume and altered mitochondrial dynamics, including the remodeling of the inner membrane to increase the density of cristae.

Conclusions

Our data demonstrate that GH likely serves a modulatory role in the metabolism of inflammatory macrophages and suggest that metabolic reprogramming of macrophages should be considered as a new target to intervene in inflammatory diseases.

Growth Hormone Stimulates Murine Macrophage Migration during Aging

BACKGROUND

Age-related impairments in macrophage functions have important consequences for the health of the elderly population. The aging process is also accompanied by a reduction in several hormones, including growth hormone (GH). Previous studies have shown that this hormone can affect macrophage activity in young individuals; however, the biological effects of GH stimulation on macrophages during aging have not yet been elucidated.

OBJECTIVE

The aim of this work was to investigate the in vitro effects of GH on peritoneal macrophages from aged mice.

METHODS

Peritoneal macrophages isolated from young (4 months-old) and old (12-15 months-old) mice were treated in vitro with 100 ng/mL of GH for 24 hours. After treatment, cells were analysed for cell morphology, reactive oxygen species (ROS) production, expression of integrins, cell adhesion to extracellular matrix molecules, and migration in transwell chambers.

RESULTS

Although GH-treated cells from old mice exhibited decreased ROS production, we did not observe the effects of GH on macrophage morphology or macrophage phagocytic activity in young and old mice-derived cell cultures. Macrophages from old mice had increased adhesion to laminin and fibronectin substrates, as did cells obtained from young mice treated with GH, but no change was observed in the expression of integrin receptors. Furthermore, cells from old mice exhibited increased migration compared to young mice and a significant increase in macrophage migration was observed under GH stimulation.

CONCLUSION

Our results showed that GH can interfere with the motility of macrophages from old mice, advancing our understanding of the interactions between the immune and neuroendocrine systems during aging.

The Modulatory Role of Growth Hormone in Inflammation and Macrophage Activation

Inflammation is a body's response to remove harmful stimuli and heal tissue damage, which is involved in various physiology and pathophysiology conditions. If dysregulated, inflammation may lead to significant negative impacts. Growth hormone (GH) has been shown responsible for not only body growth but also critical in the modulation of inflammation. In this review, we summarize the current clinical and animal studies about the complex and critical role of GH in inflammation. Briefly, GH excess or deficiency may lead to pathological inflammatory status. In inflammatory diseases, GH may serve as an inflammatory modulator to control the disease progression and promote disease resolution. The detailed mechanisms and signaling pathways of GH on inflammation, with a focus on the modulation of macrophage polarization, are carefully discussed with potential direction for future investigations.

Can plasma antioxidants prevent DNA damage in oxidative stress condition induced by growth hormone deficiency? A pilot study

Adult growth hormone deficiency (GHD), a condition characterized by increased oxidative stress, is related to augmented cardiovascular, metabolic and oncological risk. A case-control observational study has been performed to evaluate DNA oxidative damage analysing the production of thymidine-glycol in lymphocytes and its correlation with plasma antioxidant levels, evaluated as Total Antioxidant Capacity (TAC). GHD was diagnosed using GHRH 50μg iv+arginine 0,5 g/Kg test, with peak GH response <9 μg/L when BMI was <30 kg/m2 or <4 μg/L when BMI was >30 kg/m2. Three groups were identified: total GHD (n = 16), partial GHD (n = 11), and controls (n = 12). Thymidine-glycol, TAC and IGF-1 have been determined respectively in lymphocytes, plasma and serum samples. When considering thymidine-glycol, we found a significant difference between total vs partial GHD and controls. Unexpectedly thymidine-glycol was lower in total GHD, also accompanied with a significant increase in plasmatic TAC. Our results showed that in adult GHD condition, the production of antioxidant species, in response to increased oxidative stress, could exert a protective effect on thymidine-glycol formation, and consequently on DNA intracellular damages. This pilot study could be inserted in the complex scenario of oxidative damage of GHD, a subtle, yet poorly defined condition, worthy of further insights.

Evaluation of oxidative stress effects on different macromolecules in adult growth hormone deficiency

Adult growth hormone deficiency (GHD) is being increasingly recognized to cause premature mortality exacerbated by oxidative stress. A case-control observational study has been performed with the primary objective of evaluating new parameters of oxidative stress and macromolecular damage in adult GHD subjects: serum nitrotryptophan; Total Antioxidant Capacity expressed as LAG time; urinary hexanoil-lysine; urinary dityrosine and urinary 8-OH-deoxyguanosine. GHD was diagnosed using Growth Hormone-Releasing Hormone 50μg iv+arginine 0,5 g/Kg test, with a peak GH response <9 μg /L when BMI was <30 kg/m2 or <4 μg/L when BMI was >30 kg/m2. Patients affected by adult GHD were divided into three groups, total GHD (n = 26), partial GHD (n = 25), and controls (n = 29). Total Antioxidant Capacity, metabolic and hormonal parameters have been determined in separate plasma samples; nitrotryptophan in serum samples; hexanoil-lysine, dityrosine, 8-OH-deoxyguanosine in urine samples. Assessment of hexanoil-lysine exhibited a trend to increase in comparing total GHD vs partial and controls, although not significant. Values of 8-OH-deoxyguanosine did not significantly differ among the three groups. Significant lower levels of dityrosine in partial GHD vs total and controls were found. No significant difference in nitrotriptophan serum levels was found, while significantly greater values of Total Antioxidant Capacity were showed in total and partial GHD vs controls. Thus, our result confirm that oxidative stress is increased both in partial and total adult GHD. The lack of compensation by antioxidants in total GHD may be connected to the complications associated to this rare disorder.

Growth hormone-mediated reprogramming of macrophage transcriptome and effector functions

Macrophages are an important component of the innate immune response. Priming and activation of macrophages is stimulated by cytokines (i.e IFNγ). However, growth hormone (GH) can also stimulate macrophage activation. Based on these observations, the goal of this work was to 1) to compare the transcriptome profile of macrophages activated in vitro with GH and IFNγ, and 2) to assess the impact of GH on key macrophage functional properties like reactive oxygen species (ROS) production and phagosomal proteolysis. To assess the global transcriptional and functional impact of GH on macrophage programming, bone marrow derived macrophages were treated with GH or IFNγ. Our data strongly support a potential link between GH, which wanes with age, and impaired macrophage function. The notable overlap of GH with IFNγ-induced pathways involved in innate immune sensing of pathogens and antimicrobial responses argue for an important role for GH in macrophage priming and maturation. By using functional assays that report on biochemical activities within the lumen of phagosomes, we have also shown that GH alters physiologically relevant processes such as ROS production and proteolysis. These changes could have far reaching impacts on antimicrobial capacity, signaling, and antigen presentation.

Resident murine macrophage migration and phagocytosis are modulated by growth hormone

Growth hormone (GH) plays a physiological role in the immune system. In macrophages, GH enhances the production of hydrogen peroxide, superoxide anions, nitric oxide, cytokines, and chemokines, including interferon-γ and macrophage inflammatory protein-1α. However, some of the effects of GH stimulation on the biological functions of macrophages remain to be elucidated. Herein, we showed that in vivo GH treatment resulted in decreased expression of VLA-5 and VLA-6 integrins on the macrophage surface, accompanied by a reduction in macrophage adhesion to extracellular matrix (ECM) ligands, fibronectin, and laminin. Additionally, a decrease in macrophage adhesion to laminin was observed when the cells were treated in vitro with GH. In transwell migration assays, GH-treated macrophages showed increased migration after 6 h. Although in vitro GH treatment did not influence the phagocytic activity of macrophages, when the treatment was performed in vivo, peritoneal macrophages from GH-treated mice showed a higher percentage of phagocytosis and higher phagocytic capacity than cells from control animals. These results led us to analyse the role of insulin-like growth factor-1 (IGF-1), a GH stimulated factor, on macrophage phagocytosis. We observed an increase in phagocytic activity when J774 murine macrophages were treated with IGF-1 for 24 h. Our results revealed an important role for GH in resident macrophage migration and phagocytic activity. Specifically, we demonstrate that IGF-1 may be the GH stimulated factor that induces macrophage phagocytosis in vivo.

Regulation of intestinal immune response by selective removal of the anterior, posterior, or entire pituitary gland in Trichinella spiralis infected golden hamsters

The influence of anterior pituitary hormones on the gastrointestinal tract of humans and animals has been previously reported. Hypophysectomy (HYPOX) in the rat causes atrophy of the intestinal mucosa, and reduction of gastric secretion and intestinal absorption, as well as increased susceptibility to bacterial and viral infections. However, to our knowledge, no findings have been published concerning the immune response following HYPOX during worm infection, particularly that which is caused by the nematode Trichinella spiralis. The aim of this work was to analyze the effects of total or partial HYPOX on colonization of T. spiralis in the intestinal lumen, together with duodenal and splenic cytokine expression. Our results indicate that 5 days post infection, only neurointermediate pituitary lobectomy (NIL) reduces the number of intestinally recovered T. spiralis larvae. Using semiquantitative inmunofluorescent laser confocal microscopy, we observed that the mean intensity of all tested Th1 cytokines was markedly diminished, even in the duodenum of infected controls. In contrast, a high level of expression of these cytokines was noted in the NIL infected hamsters. Likewise, a significant decrease in the fluorescence intensity of Th2 cytokines (with the exception of IL-4) was apparent in the duodenum of control and sham infected hamsters, compared to animals with NIL surgeries, which showed an increase in the expression of IL-5 and IL-13. Histology of duodenal mucosa from NIL hamsters showed an exacerbated inflammatory infiltrate located along the lamina propria, which was related to the presence of the parasite. We conclude that hormones from each pituitary lobe affect the gastrointestinal immune responses to T. spiralis through various mechanisms.

A novel effect of growth hormone on macrophage modulates macrophage-dependent adipocyte differentiation

The GH receptor (GHR) is expressed on macrophages. However, the precise role of GH in regulation of macrophage function is unclear. We hypothesized that soluble factors including cytokines produced by macrophages in a GH-dependent manner regulate adipogenesis. We confirmed expression and functional integrity of the GHR in the J774A.1 macrophage cells. Conditioned medium (CM) from macrophages inhibited adipogenesis in a 3T3-L1 adipogenesis assay. CM from GH-treated macrophages decreased the inhibitory effect of CM from macrophages on adipogenesis. This effect on preadipocyte differentiation was active only during the first (early) phase of adipocyte differentiation. CM from stromal vascular compartment macrophages of mice with macrophage-specific deletion of the GHR exhibited more inhibitory effect on 3T3-L1 preadipocyte differentiation compared with CM from stromal vascular compartment macrophages of control mice, indicating that intact GH action in primary macrophages also increases preadipocyte differentiation. GH did not increase IGF-1 expression in macrophages. PCR array analysis identified IL-1beta as a candidate cytokine whose expression was altered by GH in macrophages. Levels of IL-1beta mRNA and protein were significantly decreased in GH-treated J774A.1 macrophages. Nuclear factor-kappaB stimulates IL-1beta gene expression, and GH induced a significant decrease in the levels of phosphorylated nuclear factor-kappaB in macrophages. IL-1beta is a known inhibitor of adipogenesis, and these results support GH-dependent down-regulation of macrophage IL-1beta expression as one mechanism for the observed increase in adipogenesis with CM from GH-treated macrophages. We conclude that GH decreases secretion of IL-1beta by the macrophage and thus in a paracrine manner increases adipocyte differentiation. These results provide a novel mechanism for GH's actions in the control of adipogenesis.

Production of nitric oxide by murine peritoneal macrophages in vitro on treatment with prolactin and growth hormone: Involvement of protein tyrosine kinases, Ca++, and MAP kinase signal transduction pathways

Prolactin (PRL) and growth hormone (GH) (somatotropin) have been known to possess immunomodulatory properties. In the present studies we have investigated the production of nitric oxide (NO) and TNF-alpha by murine peritoneal macrophages in vitro on treatment with PRL and GH and the signal transduction mechanism involved. It is observed that significantly enhanced production of NO is induced in macrophages on treatment with PRL and GH. It is further observed that protein tyrosine kinases, MAP kinases and Ca(++) channeling are involved in NO production by macrophages on in vitro treatment with PRL and GH. GH and PRL induced nitric oxide did not have any effect on the expression and production of TNF-alpha. PRL or GH induced TNF-alpha production by murine macrophages was insensitive in the presence of competitive inhibitor of NOS, L-NMMA. Similarly, there is no autocrine or paracrine effect of TNF-alpha on GH or PRL induced NO production and iNOS expression.

Systemic administration of IGF-I enhances healing in collagenous extracellular matrices: evaluation of loaded and unloaded ligaments

BACKGROUND

Insulin-like growth factor-I (IGF-I) plays a crucial role in wound healing and tissue repair. We tested the hypotheses that systemic administration of IGF-I, or growth hormone (GH), or both (GH+IGF-I) would improve healing in collagenous connective tissue, such as ligament. These hypotheses were examined in rats that were allowed unrestricted activity after injury and in animals that were subjected to hindlimb disuse. Male rats were assigned to three groups: ambulatory sham-control, ambulatory-healing, and hindlimb unloaded-healing. Ambulatory and hindlimb unloaded animals underwent surgical disruption of their knee medial collateral ligaments (MCLs), while sham surgeries were performed on control animals. Healing animals subcutaneously received systemic doses of either saline, GH, IGF-I, or GH+IGF-I. After 3 weeks, mechanical properties, cell and matrix morphology, and biochemical composition were examined in control and healing ligaments.

RESULTS

Tissues from ambulatory animals receiving only saline had significantly greater strength than tissue from saline receiving hindlimb unloaded animals. Addition of IGF-I significantly improved maximum force and ultimate stress in tissues from both ambulatory and hindlimb unloaded animals with significant increases in matrix organization and type-I collagen expression. Addition of GH alone did not have a significant effect on either group, while addition of GH+IGF-I significantly improved force, stress, and modulus values in MCLs from hindlimb unloaded animals. Force, stress, and modulus values in tissues from hindlimb unloaded animals receiving IGF-I or GH+IGF-I exceeded (or were equivalent to) values in tissues from ambulatory animals receiving only saline with greatly improved structural organization and significantly increased type-I collagen expression. Furthermore, levels of IGF-receptor were significantly increased in tissues from hindlimb unloaded animals treated with IGF-I.

CONCLUSION

These results support two of our hypotheses that systemic administration of IGF-I or GH+IGF-I improve healing in collagenous tissue. Systemic administration of IGF-I improves healing in collagenous extracellular matrices from loaded and unloaded tissues. Growth hormone alone did not result in any significant improvement contrary to our hypothesis, while GH + IGF-I produced remarkable improvement in hindlimb unloaded animals.

Hypophysectomy and neurointermediate pituitary lobectomy reduce serum immunoglobulin M (IgM) and IgG and intestinal IgA responses to Salmonella enterica serovar Typhimurium infection in rats

The influence of anterior pituitary hormones on the gastrointestinal tract of humans and animals has been reported. Hypophysectomy (HYPOX) in the rat causes atrophy of the intestinal mucosa, reduction of gastric secretion and intestinal absorption, and increased susceptibility to infections. To our knowledge, there are no studies on the humoral immune response of the gut-associated lymphoid tissue after HYPOX. We have reported that decreased secretion of vasopressin and oxytocin due to neurointermediate pituitary lobectomy (NIL) diminishes humoral and cell-mediated immune responses. However, no data have been published on whether NIL can affect intestinal immune responses. We analyzed the effects of HYPOX and NIL on bacterial colonization of the intestinal lumen, Peyer's patches, and spleen as well as the serum immunoglobulin G (IgG) and IgM and specific intestinal IgA levels in response to Salmonella enterica serovar Typhimurium oral infection. Results showed the following: (i) Salmonella serovar Typhimurium was eliminated from the intestinal lumen at the same rate in rats that underwent a sham operation, HYPOX, and NIL; (ii) Salmonella serovar Typhimurium colonization of Peyer's patches and spleen was significantly higher in both HYPOX and NIL rats than in sham-operated rats; (iii) serum IgG and IgM and intestinal IgA against surface proteins of Salmonella serovar Typhimurium were significantly lower in HYPOX and NIL rats than in sham-operated rats; and (iv) compared to NIL rats, higher Peyer's patch and spleen bacterial colonization and decreased IgG, IgM, and IgA production were observed in HYPOX rats. We conclude that hormones from each pituitary lobe affect the systemic and gastrointestinal humoral immune responses through different mechanisms.

From hormones to immunity: the physiology of immunology

Discoveries in the physiology of immunology have increased at an increasing rate during the past two decades. It is now recognized that the immune system is just another physiological system that regulates, and is regulated by, other physiological systems such as the brain. These advances make it clear that recent findings in genomic biology must be interpreted in the context of the environment in which animals and humans live. Lack of a strong genetic basis for significant human mental health disorders, such as major depression, points to the critical importance of interactions. Several examples of environmental x genetic x disease interactions are presented. Regulation of cells of the hematopoietic lineage by two genes that control over 80% of postnatal growth, growth hormone and IGF-I, are then highlighted. The reciprocal relationship of how proinflammatory cytokines from the immune system regulate the growth hormone/IGF-I axis is also summarized. Particular emphasis is placed upon TNFalpha-induced IGF-I resistance in neurons, muscle cells and epithelial cells. This cytokine regulation of hormone action may ultimately be more important for human and animal health than direct effects of growth hormone and IGF-I on hematopoietic cells. Wasting of AIDS patients is given as an important clinical example of how TNFalpha from an activated immune system reduces IGF-I sensitivity in multiple physiologic systems, including muscle, nervous and hematopoietic tissues.

Enhancement of immunocompetence in tuberculosis by DNA vaccination

Our studies in mice show that DNA vaccines, initially designed to prevent infection, can have a dramatic therapeutic action too. In heavily infected mice, simply by giving DNA vaccination, the immune response can be caused to switch from one that is relatively inefficient and gives bacterial stasis to one that kills the bacteria, and persistent bacteria can be eliminated. Adoptive transfer of protection with T cell clones and in vitro tests of clone function indicate that the effects are probably mainly mediated by antigen specific CD8+/CD4-/CD44hi T cells that both produce gamma-interferon and kill the bacteria during granule-dependent lysis of infected macrophages. We can speculate that application of such immunotherapy in conjunction with conventional chemotherapeutic antibacterial drugs might result in faster or more certain cure of the disease in man. Furthermore, similar vaccines used prophylactically and therapeutically might be able to both prevent establishment of this persistent state and eliminate it if it is already established.

NADPH dependent superoxide generation in the ovary and uterus of mice during estrous cycle and early pregnancy

NADPH dependent O2- production in the ovary and uterus of cycling and pregnant mice was estimated employing a novel technique of time-lapse electron spin resonance enhancement of a superoxide-trapping spin trap. The NADPH dependent O2- generation in the mouse ovary increased during the early pre-ovulatory phase in cycling females and during extended luteal phase in pregnant animals. A peak of uterine NADPH dependent O2- production at proestrous in the cycling animals at pre-implantation phase in pregnant animals suggested a contribution of this enzyme towards generating high levels of superoxide anion radical during the respective stages. Both ovarian and uterine NADPH dependent O2- production appeared to be LH-inducible.

Role of cytokines and nitric oxide in the induction of tuberculostatic macrophage functions

The aim of this study was to determine phenotypic differences when BCG invades macrophages. Bacilli prepared from the same BCG primary seed, but produced in different culture media, were analysed with respect to the ability to stimulate macrophages and the susceptibility to treatment with cytokines and nitric oxide (NO). Tumour necrosis factor (TNF) activity was assayed by measuring its cytotoxic activity on L-929 cells, interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) were assayed by enzyme-linked immunosorbent assay (ELISA), whereas NO levels were detected by Griess colorimetric reactions in the culture supernatant of macrophages incubated with IFN-gamma, TNF or NO and subsequently exposed to either BCG-I or BCG-S. We found that BCG-I and BCG-S bacilli showed different ability to simulate peritoneal macrophages. Similar levels of IL-6 were detected in stimulated macrophages with lysate from two BCG samples. The highest levels of TNF and IFN-gamma were observed in macrophages treated with BCG-S and BCG-I, respectively. The highest levels of NO were observed in cultures stimulated for 48 h with BCG-S. We also found a different susceptibility of the bacilli to exogenous treatment with IFN-gamma and TNF which were capable of killing 60 and 70% of both bacilli, whereas NO was capable of killing about 98 and 47% of BCG-I and BCG-S, respectively. The amount of bacilli proportionally decreased with IFN-gamma and TNF, suggesting a cytokine-related cytotoxic effect. Moreover, NO also decreased the viable number of bacilli. Interestingly, NO levels of peritoneal macrophages were significantly increased after cytokine treatment. This indicates that the treatment of macrophages with cytokines markedly reduced bacilli number and presented effects on NO production. The results obtained here emphasize the importance of adequate stimulation for guaranteeing efficient killing of bacilli. In this particular case, the IFN-gamma and TNF were involved in the activation of macrophage bactericidal activity.

Induction of apoptosis in murine macrophages by Mycobacterium tuberculosis is reactive oxygen intermediates-independent

Infection with Mycobacterium tuberculosis induces apoptosis in murine macrophage lines. Resistant macrophages B10R (Bcgr) are more prone to undergo apoptosis than susceptible B10S (Bcgs) macrophages. Apoptosis and inhibition of intracellular growth of the mycobacteria seem to be dependent on the production of nitric oxide, since both can be reverted by aminoguanidine (AMG). Although B10R macrophages produce more superoxide anion than B10S macrophages after infection with M. tuberculosis, reactive oxygen intermediate (ROIs) scavengers did not affect uptake of 3H-uracil incorporation by the mycobacteria nor the induction of apoptosis. These results further suggest that both phenomena are dependent on the production of nitric oxide by the infected macrophages.

Human growth hormone locally released in bone sites by calcium-phosphate biomaterial stimulates ceramic bone substitution without systemic effects: a rabbit study

Calcium-phosphate bone replacement biomaterial has been used as a drug carrier for therapeutic agents. This study investigated the efficacy of local administration of human growth hormone (hGH) by macroporous biphasic calcium phosphate (MBCP) implants in improving the bone substitution qualities of ceramics. hGH release from MBCP implants loaded with 1 microg of hGH was rapid during the first 48 h and then sustained for a total of 9 days. Immunolocalization of hGH in vitro and in vivo by transmission electron microscopy showed its presence inside the material, indicating that it was able to penetrate within the porosity of the ceramic during the adsorption process. MBCP cylinders (6 x 6 mm) were loaded with 0.1, 1, and 10 microg of hGH and implanted into rabbit femurs (n = 40). The effects of locally released hGH on bone ingrowth and ceramic resorption were evaluated by scanning electron microscopy and image analysis. The results indicated that hGH increased bone ingrowth (+65%) and ceramic resorption (+140%) significantly in comparison with control implants and that the increase was dose dependent. Biochemical parameters monitored in rabbit plasma and urine, as well as the absence of any significant difference between contralateral implants and the control, indicated that hGH did not produce detectable systemic effects. Thus, the use of MBCP appears to be effective for local delivery of hGH, resulting in improved bone substitution.

Differential potentiation of anti-mycobacterial activity and reactive nitrogen intermediate-producing ability of murine peritoneal macrophages activated by interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha)

The anti-mycobacterial activities of IFN-gamma and TNF-alpha-treated murine peritoneal macrophages were determined. Resident macrophages pretreated with IFN-gamma or TNF-alpha for 2 days were infected with test organisms and subsequently cultured for up to 7 days. First, the early-phase growth of Mycobacterium tuberculosis (days 0-3) was strongly suppressed in IFN-gamma-treated macrophages, and progressive bacterial elimination was subsequently observed. Although TNF-alpha treatment of macrophages did not affect the early phase growth of organisms, bacterial killing was observed in the later phase of cultivation. Second, although IFN-gamma-treated macrophages killed M. avium during the first 3 days of culture, regrowth of the intracellular organisms was subsequently observed. TNF-alpha treatment of macrophages did not influence the mode of intracellular growth of M. avium. Third, IFN-gamma but not TNF-alpha enhanced production of reactive nitrogen intermediates (RNI) by macrophages infected with M. tuberculosis or M. avium, whereas both cytokines increased macrophage release of reactive oxygen intermediates (ROI). The present findings therefore show that IFN-gamma and TNF-alpha potentiated the anti-mycobacterial activity of murine peritoneal macrophages in different fashions. They also suggest that RNI played more important roles than did ROI in the expression of macrophage anti-mycobacterial, particularly anti-M. avium, activity.

Identification and characterization of protective T cells in hsp65 DNA-vaccinated and Mycobacterium tuberculosis-infected mice

Immunization by intramuscular injection of plasmid DNA expressing mycobacterial 65-kDa heat shock protein (hsp65) protects mice against challenge with virulent Mycobacterium tuberculosis H37Rv. During infection or after immunization, CD4+/CD8- and CD8+/CD4- hsp65-reactive T cells increased equally in spleens. During infection, the majority of these cells were weakly CD44 positive (CD44(lo)) and produced interleukin 4 (IL-4) whereas after immunization the majority were highly CD44 positive (CD44(hi)) and produced gamma interferon (IFN-gamma). In adoptive transfer of protection to naive mice, the total CD8+/CD4- cell population purified from spleens of immunized mice was more protective than that from infected mice. When the cells were separated into CD4+/CD8- and CD8+/CD4- types and then into CD44(hi) and CD44(lo) types, CD44(lo) cells were essentially unable to transfer protection, the most protective CD44(hi) cells were CD8+/CD4-, and those from immunized mice were much more protective than those from infected mice. Thus, whereas the CD44(lo) IL-4-producing phenotype prevailed during infection, protection was associated with the CD8+/CD44(hi) IFN-gamma-producing phenotype that predominated after immunization. This conclusion was confirmed and extended by analysis of 16 hsp65-reactive T-cell clones from infected mice and 16 from immunized mice; the most protective clones, in addition, displayed antigen-specific cytotoxicity.