An analysis of the natural killer cell defect in beige mice

Inhibition of tumor necrosis factor alpha alters resistance to Mycobacterium avium complex infection in mice

Increased production of tumor necrosis factor alpha (TNF-alpha) appears to play an important role in the progression of human immunodeficiency virus disease. One treatment strategy being explored is the use of TNF-alpha inhibitors. TNF-alpha also appears to be important in conferring resistance to infections, and the inhibition of this cytokine may exacerbate the emergence of opportunistic pathogens, such as Mycobacterium avium complex (MAC). The present study examines the possibility that inhibition of TNF-alpha will increase the progression of disease in mice infected with MAC. C57BL/6 beige (bg/bg) mice have been shown to be highly susceptible to infection with MAC and are routinely used for testing of antimycobacterial drugs. However, bg/bg mice are known to exhibit impaired phagocyte and natural killer cell function. Since these cell types are important sources of TNF-alpha, the susceptibility of the bg/bg strain to infection with MAC was compared with those of the heterozygous (bg/+) and wild-type (+/+) strains of C57BL/6 mice. The susceptibilities of the bg/bg and bg/+ strains of mice infected with MAC were found to be comparable. The +/+ strain was the least susceptible. Mycobacterial burden and serum TNF-alpha levels increased over time in all the strains of mice tested. The bg/+ strain of C57BL/6 mice was then chosen to measure the activity of TNF-alpha antagonists. Treatment with dexamethasone decreased serum TNF-alpha levels and increased mycobacterial burden. Treatment with anti-TNF-alpha antibody or pentoxifylline did not significantly alter serum TNF-alpha levels but increased mycobacterial burden. Treatment with thalidomide neither consistently altered mycobacterial burden in the spleens or livers of infected mice nor affected serum TNF-alpha levels.

Susceptibility of beige mice to Mycobacterium avium: role of neutrophils

The beige mutation in C57BL/6 mice has been shown to increase the susceptibility to infection by Mycobacterium avium. In this study, we confirmed those results and showed that the effect of the beige mutation was most obvious after infection with a strain of lower virulence than with a highly virulent isolate of M. avium. The dissemination of M. avium from the gut was observed with both C57BL/6 and beige mice but was faster in the latter. The expression of gamma interferon (IFN-gamma) and the priming for tumor necrosis factor production during an in vivo infection were similar between beige and immunocompetent C57BL/6 mice. IFN-gamma produced during the infection of beige mice was protective in the spleen, and the administration of recombinant IFN-gamma restored the resistance in the spleen to levels similar to those found in control mice. There were no histological differences between wild-type and beige mice with respect to granuloma formation in the liver. The increased susceptibility of beige mice to M. avium as manifested in the liver was reduced by transfusing neutrophils from wild-type C57BL/6 mice. Likewise, depletion of neutrophils from C57BL/6 mice rendered them as susceptible to M. avium infection of the liver as beige mice. Our results point to the participation of neutrophils in the defect of beige mice in addition to other defects. Furthermore, these results show that neutrophils play a significant role in the defense mechanisms against mycobacterial infections and that beige animals may be a useful model for study of the role of neutrophils in mycobacteriosis.

Natural killer cell regulation of murine embryonic pulmonary fibroblast survival in vivo

We examined the role of the natural killer (NK) cell in controlling the survival of embryonic pulmonary fibroblasts in vivo. In vitro, both primary embryonic fibroblasts and an embryonic fibroblast line (10T1/2) were lysed by syngeneic C3H/HeN splenocytes threefold more efficiently than primary adult fibroblasts. The membrane phenotype of the effector cells was typical of NK cells. It was asialo GM1+, Lyt2.1-, Lyt 1.1-, Thy 1.2-. The cytotoxicity of the effector cell could be enhanced by IFN-alpha/beta but was deficient in the C3H/HeJ bg/bg mutant. Iododeoxyuridine (131I-dUrd)-labeled embryonic fibroblasts were injected intravenously into syngeneic mice with either enhanced or deficient NK function and their survival in the lung was quantitated. Enhanced fibroblast survival was detected in the NK deficient C3H/HeJ beige (bg/bg) mutant strain compared to its normal littermate C3H/HeJ (bg/+). A second method of NK depletion by pretreatment with rabbit anti-asialo GM1 antiserum also produced a striking increase in fibroblast survival. Poly(I:C) significantly enhanced the elimination of pulmonary fibroblasts from the lung between 4 and 24 hr after injection. Poly(I:C) did not enhance clearance of pulmonary fibroblasts in the C3H/HeJ (bg/bg) mutant, but did so in the normal littermate C3H/HeJ (bg/+). In conclusion, we have shown that the survival of embryonic pulmonary fibroblasts was inversely correlated with in vivo NK activity suggesting a possible role for this cytotoxic cell in the control of fibroblast growth in vivo.

The adjuvant effect of a muramyl dipeptide (MDP) analog on temperature-sensitive Salmonella mutant vaccine

Adjuvant effect of a synthetic muramyl dipeptide analog, MDP-Lys (L18), MurNAc-L-Ala-D-glu[Lys(CO-(CH2)16-CH3)-OH]NH2 on a live Salmonella enteritidis vaccine, a temperature-sensitive mutant Ts-O strain that was obtained from the virulent S. enteritidis No.11 strain and could not grow at 37 degrees C, but could multiply at 25 degrees C as fast as the parent strain, was examined. Although the Ts-O organisms were avirulent and could hardly multiply in vivo when the organisms were injected into C57BL/6 mice and its mutant beige strain, which has a malfunction of phagocytic cells, injection of these mice with Ts-O endowed them with some protective immunity against infection by the virulent No.11 strain. When MDP-Lys(L18) was injected with Ts-O vaccine, the protection and the bactericidal capacity in the peritoneal cavities and spleens of these mice were augmented. MDP-Lys(L18) was still effective when it was injected at 48 h before or after the inoculation of Ts-O vaccine. Its effect was also observed against infection by the virulent S. cholerae-suis Hokkaido strain, a strain that does not share common O-antigenic determinants with the S. enteritidis No.11 or Ts-O strain. In addition, the mice that were inoculated simultaneously with Ts-O organisms and MDP-Lys(L18) were examined 10 days later for their footpad delayed type hypersensitivity reactions against Ts-O antigen. Mice inoculated with MDP-Lys(L18) and Ts-O showed augmented footpad swelling in comparison with the controls. These findings indicate that MDP-Lys(L18) is capable of augmenting the cellular immunity by live vaccine.

The genetic background modulates the effect of the beige gene on susceptibility to cytomegalovirus infection in mice

Homozygous beige (bg/bg) mice were more susceptible to the development of fatal disease induced by murine cytomegalovirus (MCMV) than their bg/ + littermates. However, the increase in susceptibility depended on the genetic background of the strain carrying the bg gene. C57BL/6, SB/Le, DBA/2, and CBA bg/bg mice showed, respectively, 2.5-, 3.2-, 9.5-, and 18.6-fold increases in susceptibility compared with the corresponding bg/+ animals. Beige mice showed higher liver titres of MCMV than bg/ + by the 2nd or 3rd day after infection, and tissue damage was also greater. Splenic NK cells were not detected in uninfected bg/bg mice, and after virus inoculation the increment in cytotoxicity was greater in bg/ + than in bg/bg mice. However, cytotoxicity towards WEHI-164 cells was not impaired in bg/bg mice and was not augmented by MCMV. Interferon titres were also not impaired by the beige mutation. Of the strains examined, CBA had the highest endogenous levels of NK cells and were most genetically resistant to MCMV. Thus, our observation that the beige gene had the greatest effect on susceptibility in this strain suggests that NK cells are important mediators of genetically determined resistance to MCMV.

Effect of muramyl dipeptide analog on Salmonella enteritidis infection in beige mice with Chediak-Higashi syndrome

Beige mutant (bg/bg) mice with Chediak-Higashi syndrome (CHS) were much more sensitive to virulent Salmonella enteritidis No. 11 strain than parental C57 BL/6 (+/+) or heterozygous (bg/+) mice, and they had weaker bactericidal activity against the organisms. Muramyl dipeptide (MDP) and N alpha-(N-acetyl-muramyl-L-alanyl-D-isoglutamyl)-N epsilon-stearoyl-L-lysine [MDP-Lys(L18)], a synthetic derivative of MDP, failed to confer any protection against the infection, but the MDPs showed some ability to stimulate the bactericidal activity in the peritoneal cavities and spleens of these mice. The bactericidal effect of MDP-Lys(L18) was dose-dependent, and the greatest effect was seen when it had been injected 24 hr before the infection. Multiple injections of MDP were much more beneficial than a single injection. Previous injection of N2,O2'-dibutyryl guanosine 3' : 5'-cyclic monophosphate (DB-cGMP) improved the impaired bactericidal capacity in beige mice, but the simultaneous injection of N6,O2-dibutyryl adenosine 3' : 5'-cyclic monophosphate (DB-cAMP) with DB-cGMP abolished the effect of DB-cGMP. The augmentation of bactericidal capacity by MDP-Lys(L18) was not affected by the injection of either DB-cGMP or DB-cAMP, suggesting that the effect of the MDPs was not related directly to cyclic nucleotide regulation in beige mice.

Natural cytotoxic cells against solid tumors in mice. IV. Natural cytotoxic (NC) cells are not activated natural killer (NK) cells

Natural cell-mediated cytotoxicity (NCMC), measured against a variety of tumors, is mediated by at least two sub-populations of effector cells: natural cytotoxic (NC) and natural killer (NK). The studies described in this report show that target lysis by NC cells requires a prolonged (18- to 24 h) assay period, whereas NC-susceptible targets can be lysed in short-term (4h) [3H]-proline assays using allo-sensitized CTL or mitogen-activated cytotoxic populations. NC cells are not "activated" during the long-term assay as indicated by: (1) demonstrating that lysis of NC-susceptible targets in long-term (20 h) 51Cr assays is still the function of a Qa-5- effector cell (NC) and (2) the fact that preincubation of the NC effector cell with susceptible targets for 18 h did not result in the activation of an NK-like population (kinetics of target lysis were comparable to those noted with fresh NC cell preparations). We show that NC cell activity is preserved in both the beige mutant and the PL/J mouse strains, both of which exhibit low NK cell activity, even in long-term assays. These combined studies support the view that NC and NK cell activities are the function of distinct cell types and not the property of a single cell class under different states of activation.

Resistance to infections in mice with defects in the activities of mononuclear phagocytes and natural killer cells: effects of immunomodulators in beige mice and 89Sr-treated mice

Beige mice, which are a homolog of the Chediak-Higashi syndrome, and mice treated with 89Sr to destroy the bone marrow provide animal models of defects in mononuclear phagocyte and natural killer cell functions. The innate resistance of these mice to viruses such as herpes simplex and encephalomyocarditis viruses, however, is normal. Moreover, treatment of the mice with immunomodulators such as Propionibacterium acnes (formerly designated Corynebacterium parvum) and pyran produced a significant increase in resistance to encephalomyocarditis virus. The antiviral effect of P. acnes in 89Sr-treated mice was exhibited during marked monocytopenia and without evidence for an inflammatory influx of macrophages into the peritoneal cavity. Treatment with P. acnes was also effective in increasing the resistance of beige mice to infection with Listeria monocytogenes. Thus, immunomodulators can be effective in mice that exhibit impaired macrophage and natural killer cell functions.