Antibacterial mechanisms of the lower respiratory tract. I. Immunoglobulin synthesis and secretion

Immunoglobulin synthesis and secretion have been studied in the rabbit lower respiratory tract, both in the normal state and after infection with Diplococcus pneumoniae or Listeria monocytogenes. In vitro synthesis of immunoglobulin and specific antibody was assessed by incorporation of 14C-labeled amino acids into protein. Lower respiratory tract secretions and serum were analyzed for immunoglobulin and antibody against the infecting organism. Normal respiratory tract produced small quantities of immunoglobulin, most of which was IgG. After bacterial infection of the lower respiratory tract, there was a marked increase in local synthesis of immunoglobulin, especially IgG. Specific antibody of IgG class was produced in all lungs infected with listeria by the 11th day, and in lungs infected with pneumococcus by the 8th day. Secretions from all normal and infected lower respiratory tracts contained IgA and IgG. The IgA to IgG ratios in secretions of normal animals, and animals infected with listeria or pneumococcus, were 2.3, 2.5, and 2.6, respectively. Sera of animals infected with L. monocytogenes contained specific antibody of IgG class but lacked IgA antibody, whereas secretions had both IgA and IgG class antibody against listeria. Similarly, sera of animals infected with D. pneumoniae had IgG class antibody but no IgA antibody, whereas only IgA antibody was found in secretions. The evidence that locally synthesized immunoglobulin (especially IgA), including specific antibody, is secreted into the lower respiratory tract lumen is discussed. Further definition of the role of "local" antibacterial antibody in the respiratory tract is of considerable importance.

Congenital mycosis (Candida albicans)

Four new cases of congenital mycosis are described. Fifteen cases were found in the litterature. Although this fetal infection appears to be scarce, its frequency is probably underestimated. Because of the nature of lesions, it is possible to assume that <i>Candida albicans</i> ascends from the vagina through clinically undamaged membranes. The newborn may be a well-developed term baby, a premature, or a small-for-date baby; even miscarriage may happen. The physiopathology of this infection is discussed.

Listeriosis in newborn swine

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Rapid method for the isolation of Listeria monocytogenes from experimentally infected mice

Listeria monocytogenes was successfully isolated from experimentally infected mice by placing homogenized tissues in phosphate-buffered saline (PBS), trypsin, peptone, or pepsin followed by incubation at 37 C for 24 hr. A larger number of Listeria isolates were recovered from the trypsin or PBS splenic homogenate suspensions incubated at 37 C for 2 hr than from the other diluent suspensions. Holding infected tissues at 4 C for at least 3 months did not increase the efficiency of Listeria isolation. Listeria L-forms were not isolated from mice injected with the bacterial form. The in vitro viability of Listeria L-forms suspended in PBS or PBS splenic homogenate was greatly reduced when held at 4 C.

The relative importance of blood monocytes and fixed macrophages to the expression of cell-mediated immunity to infection

Infection in mice with Listeria monocytogenes results in a substantial accumulation of migrant macrophages in the liver. The immigrant cells populate both the infective foci and intervening sinusoids. They have the labeling characteristics of blood monocytes, and their appearance in infective foci in the liver corresponds to the expression of a high level of antimicrobial immunity in this organ. The infected liver acquires additional new macrophages by Kupffer-cell division. The proliferation of these cells, however, is not essential for the expression of immunity in the liver. The results indicate that the macrophages which express immunity to a primary infection with L. monocytogenes are those derived from circulating monocytes. Most of these cells are quickly lost once the parasite is eliminated from the tissues.

Suppression of cell-mediated immunity to infection by an antimitotic drug. Further evidence that migrant macrophages express immunity

The development of acquired cell-mediated immunity to infection with Listeria monocytogenes can be blocked by a 15 hr pulse of the antimitotic drug, vinblastine (Vb). The drug has no effect on the host-parasite relationship after 72 hr of infection when a high level of immunity is being expressed, i.e., when infective foci are populated by activated macrophages. Infective foci in mice treated early during infection with Vb do not acquire migrant macrophages, but they become acellular after 48 hr of infection. The results indicate that Vb destroys the dividing precursors of migrant macrophages. The possibility that Vb prevents the activation of these cells by destroying dividing lymphoid cells engaged in the specific immunological phase of the host response is also considered.

Histopathology of Listeria monocytogenes after oral feeding to mice

Ingestion by mice of Listeria monocytogenes in drinking water induced micro-abscesses of the liver and ulcerative enteritis. In pregnant mice, these lesions were larger and more extensive than in nonpregnant female and male mice. Pregnancy is interrupted by a purulent panmetritis and necrotizing placentitis. The early microabscess is unique in that it consists of monocytic cells with bizarre-shaped nuclei. The experimentally induced pathological changes in livers and intestines of mice used in this study are similar to those observed in listeric neonatal septicemia of human infants.