Publications

Mycobacterium leprae, an obligate intracellular pathogen, invades and multiplies within host mononuclear phagocytes. To understand M. leprae invasion better, we have investigated the role of phagocyte receptors and bacterium-bound ligands in phagocytosis of M. leprae by human monocytes. Complement receptors CR1 and CR3 mediate adherence and phagocytosis of M. leprae in nonimmune serum. Two MAbs used in combination against CR3 inhibit adherence by up to 90 +/- 3%. Two MAbs used in combination against CR1 and CR3 inhibit adherence by up to 70 +/- 1%. Single MAbs against CR1 or CR3 consistently inhibit adherence by 38-55%. In contrast, MAbs against other monocyte surface molecules, alone or in combination, do not significantly influence adherence. As studied by electron microscopy, 100% of monocyte-associated M. leprae are ingested in the presence of nonimmune serum and MAbs against CR3 markedly inhibit ingestion. Complement receptors CR1 and CR3 also mediate the low level of adherence observed in the absence of serum. Serum complement component C3 serves as a ligand on the bacterial surface in monocyte phagocytosis of M. leprae. Adherence of M. leprae to monocytes is enhanced by preopsonization (3.1 +/- 1.1-fold increase) and is markedly reduced in less than 0.5% fresh serum (66 +/- 7% reduction) or heat-inactivated serum (68 +/- 3% reduction). Adherence is also markedly reduced in C3- or factor B-depleted serum; repletion with purified C3 or factor B increases adherence 4.3 +/- 0.8- and 2.6 +/- 0.2-fold, respectively. C3 is fixed to M. leprae by the alternative pathway of complement activation, as determined by a whole bacterial cell ELISA. By electron microscopy, monocytes ingest M. leprae by conventional phagocytosis. This study demonstrates that (a) human monocyte complement receptors CR1 and CR3 mediate phagocytosis of M. leprae; (b) complement component C3 on the bacterial surface serves as a ligand for complement receptors; (c) complement component C3 binds to M. leprae by the alternative pathway of complement activation; and (d) monocytes phagocytize M. leprae by conventional phagocytosis.

We have examined the receptor-ligand interactions and the method of phagocytosis of virulent Mycobacterium tuberculosis by human monocytes. mAb against complement receptors (CR) inhibit adherence and phagocytosis of M. tuberculosis in fresh nonimmune serum. A mAb against the type 1 CR (CR1) inhibits adherence of M. tuberculosis by 40 +/- 5%, and three different mAb against the type 3 CR (CR3) each inhibit adherence by 39 +/- 5% to 47 +/- 4%. A mAb against CR1 used in combination with one of the three mAb against CR3 inhibits adherence by up to 64 +/- 7%. Most strikingly, two mAb used in combination against CR3 inhibit adherence by up to 81 +/- 2%. mAb against other monocyte surface Ag do not significantly influence adherence. In like fashion, mAb against CR but not other monocyte surface Ag inhibit adherence of preopsonized M. tuberculosis in the presence of heat-inactivated serum. By electron microscopy, monocytes ingest all M. tuberculosis that adhere in the presence of nonimmune serum; mAb against CR3 markedly inhibit ingestion. In contrast to CR, the FcR and the beta-glucan-inhibitable receptor for zymosan play little or no role in mediating M. tuberculosis adherence or ingestion. Adherence of M. tuberculosis is serum-dependent, requiring greater than or equal to 2.5% serum for optimal adherence. Heat inactivation of serum markedly reduces adherence of M. tuberculosis (75.5 +/- 7%) and preopsonization of bacteria enhances adherence by 2.9 +/- 0.4-fold. Adherence is also markedly reduced in C3- or factor B-depleted serum; repletion with C3 or factor B increases adherence by 2.1 +/- 0.4-fold and 1.86 +/- 0.05-fold, respectively. Fab anti-C3 IgG markedly inhibits monocyte adherence of preopsonized M. tuberculosis (71 +/- 1%). C component C3 is fixed to M. tuberculosis by the alternative C pathway as determined by a whole bacterial cell ELISA. Human monocytes ingest M. tuberculosis by conventional phagocytosis as viewed by electron microscopy. This study demonstrates that human monocyte CR1 and CR3 mediate phagocytosis of M. tuberculosis and C component C3 in serum is acting as the major bacterium-bound ligand.

Separate groups of rats were given 30 pairings of a light (conditioned stimulus, CS) and 500-ms shock (unconditioned stimulus, US) at CS-US intervals of 0, 25, 50, 100, 200, 800, 3,200, 12,800, or 51,200 ms. Other groups had lights and shocks inconsistently paired. The startle reflex was elicited 2-4 days later with a noise burst alone or 25-51,200 ms after light onset. After CS-US pairings over a wide range of intervals (25-51,200 ms), startle was potentiated in testing, sometimes as rapidly as 50 ms after light onset. Magnitude of potentiation and resistance to extinction were generally greater with longer CS-US intervals. In several groups, potentiation was maximal at a test interval that matched the CS-US interval used in training. This temporal specificity sharpened with increasing numbers of training trials but even occurred with a single training trial in which a 51,200-ms CS-US interval was used. The data indicate that even during simple fear conditioning, animals rapidly learn a temporal CS-US relationship. This has important implications for understanding the neural mechanisms of fear conditioning.

In an effort to ascertain important epidemiologic and prognostic risk factors, we analyzed 33 cases of Staphylococcus aureus meningitis occurring over an 8-year period (1976 to 1984). Staphylococcus aureus caused 6% of all bacterial meningitis at our University Hospital. Fifty percent of cases were pediatric and included 7 newborn infants, of whom 71% were either premature or had low birth weight. Major underlying diseases were: central nervous system (CNS) disorders (55%), endocarditis (21%, predominantly intravenous drug abusers), other sites of infection (27%), and prematurity (24%). Fifty-seven percent of patients were bacteremic and 41% of those had concomitant bacteriuria. Hypoglycorrhachia was present in 27% of cases, positive cerebrospinal fluid (CSF) Gram stain in 20%, disseminated intravascular coagulation (DIC) in 19%, and methicillin-resistant organisms in 18%. Cerebrospinal fluid cultures remained positive for a protracted period (mean, 6.7 days) regardless of the presence or absence of a CNS shunt. Overall mortality was 21%. Favorable outcomes were associated with the eventual presence of sterile CSF (15.4% vs. 100% mortality) and the removal of foreign bodies (10% vs. 67% mortality). Mortality was also associated (p less than 0.5) with the presence of diabetes mellitus, age greater than 60, obtundation or coma on presentation, bacteremia, or DIC. Cure correlated (p less than .05) with CNS shunt-associated infections, age less than 1, normal neurologic examinations on presentation, or the absence of DIC or bacteremia.(ABSTRACT TRUNCATED AT 250 WORDS)