Monocyte phagocytosis of opsonized Neisseria meningitidis serogroup B.

The chemiluminescence (CL) was examined when peripheral blood monocytes were incubated with opsonized Neisseria meningitidis, serogroup B, serotype 15:P1.16 or serotype 2a:P1.2. The monocytes were separated from a mononuclear cell suspension by an immunomagnetic negative selection technique using magnetic polystyrene microspheres coated with monoclonal antibodies specific for T and B lymphocytes. More than 90% of the lymphocytes were removed, yielding a suspension containing 93% monocytes. Optimal sensitivity for phagocytosis was obtained using 1% serum (10 microliters), 72 bacteria per monocyte cell, and 7.5 min opsonization and incubation time during continuous agitation at 37 degrees C. The CL was amplified by lucigenin. Preliminary experiments suggest that convalescent sera from patients with group B meningococcal disease induced increased CL responses compared to acute sera. Sera from volunteers immunized with an outer membrane complex vaccine from serogroup B, serotype 15:P1.16 or 2a:P1.2 meningococci also induced increased CL activity compared to preimmune sera. No such response was shown when a group B capsular polysaccharide vaccine was given. This response pattern was also demonstrated by a flow cytometric phagocytosis technique (FCM). Internalization of meningococci by monocytes was demonstrated by a FCM quenching technique and by transmission electron microscopy. CL and FCM represent rapid and reproducible methods for the measurement of opsonophagocytosis of meningococci by monocytes and may be performed with minute amounts of sera.

In vivo and in vitro effects of doxycycline on leucocyte membrane receptors.

Tetracyclines, particularly doxycycline, have adverse effects on granulocyte function in vitro. We have examined the effects of doxycycline on membrane receptors for IgG (Fc gamma-R) and C3b (C3b-R) on granulocytes and lymphocytes, as well as on the sheep erythrocyte receptor (E-R) on T lymphocytes. Acne patients given doxycycline orally had a lower percentage of Fc gamma-R positive granulocytes (57%) than before treatment (80%) or compared to healthy controls (81%). Following in vitro doxycycline incubation, normal granulocytes showed decreased levels of Fc gamma-R positive cells. This effect was counteracted by the addition of magnesium during incubation. The deleterious effect of doxycycline on granulocyte functions may be due to decreased levels of Fc gamma-R bearing granulocytes. Doxycycline in vivo or in vitro had no significant effect on the proportion of C3b-R bearing granulocytes or lymphocytes or the T lymphocyte percentage. After in vitro irradiation with light at 340-380 nm, however, both granulocytes and lymphocytes preincubated with doxycycline showed up to 50% decrease in Fc gamma-R bearing cells, while control cells without doxycycline were unaffected.

Leukocyte membrane receptors in meningitis and other bacterial infections.

Blood leukocytes from 37 patients with acute bacterial infections, and cerebrospinal fluid (CSF) granulocytes from 12 patients with bacterial meningitis, were examined for the distribution of membrane receptors (R) for (1) untreated sheep erythrocytes (E), (2) the Fc portion of IgG (Fc gamma), and (3) complement component C3b. We found a decreased percentage of granulocytes bearing Fc gamma-R in the CSF from patients with meningitis, and in blood from patients with respiratory tract infections. This group also had a decreased percentage of C3b-R bearing granulocytes on admission, whereas meningitis patients had lower levels of C3b-R and Fc gamma-R bearing granulocytes in the 2nd and 3rd week and even later. Several patients with meningitis and gastroenteritis had granulocytes bearing the E-R, previously considered specific for T lymphocytes. Such cells were also found in the CSF. Meningitis and respiratory tract infections were associated with a decreased percentage of 'active' T lymphocytes. The total percentage of T lymphocytes was also decreased in meningitis. Conversely the proportion of Fc gamma-R bearing lymphocytes (consisting mostly of B lymphocytes) was increased in most infections. During the first 3 weeks of bacterial meningitis, the percentages of Fc gamma- and C3b-R bearing granulocytes, and of Fc gamma-R bearing lymphocytes, gradually decreased, while the T lymphocyte percentage increased from the initial low values.

Untreated meningococcemia in two siblings.

In September 1982 two siblings were admitted to hospital within a few days of each other, with almost identical symptoms of meningococcemia. One of them had been discharged from hospital four days previously, fully treated to meningococcal meningitis. Two systemic meningococcal isolates and nasopharyngeal meningococci from patient No 1 were B:15:P1. 16 strains as well as one nasopharyngeal isolate from patient No 2. One nasopharyngeal isolate from the father was a non-encapsulated 15:P1. 16 strain. The two systemic isolates were clearly different with respect to the class 5 outer membrane protein(s); the second closely resembled the various nasopharyngeal isolates, all of which were identical. Only the two patients mounted detectable bactericidal antibody activity as measured by using human complement. Convalescent serum from patient No 1 after the second episode was bactericidal against the first but not the second isolate. No differences among patients and parents were found by measuring opsonizing activity. The clinical picture and the laboratory results seem to indicate that both children, one after a treated meningitis episode, had benign meningococcemia which subsequently ran its course untreated and without complications.