Effect of protein A on the antistaphylococcal defence mechanisms of the murine lung

The importance of IgG attached to protein A in the initial reaction of inspired Staphylococcus aureus and alveolar macrophages was studied by infecting unimmunized mice with aerosols of S. aureus strains 566 and Wood 46 with high and low protein A content. At 2, 4, and 8 hr after infection, the presence of IgG attached to S. aureus and rates of staphylococcal ingestion and killing by macrophages were determined. IgG was detected by staining of sections of the right lung with fluorescein-labeled goat antibody to mouse IgG. For S. aureus strain 566, 25%--40% of the total number of bacteria, as determined in equivalently sized subjacent sections stained by the Brown and Brenn tissue gram stain, contained attached IgG. A few S. aureus strain Wood 46 were surrounded by dimly fluorescing complexes. Since rates of bacterial ingestion and killing were similar for both strains in this in vivo model of infection, IgG binding to protein A does not affect the bactericidal capacity of alveolar macrophages.

Lymphocyte responsiveness to Pseudomonas aeruginosa in cystic fibrosis: Relationship to status of pulmonary disease in sibling pairs

Lymphocyte proliferative responses to Pseudomonas aeruginosa and Staphylococcus aureus were evaluated in six sibling pairs with cystic fibrosis. In each pair, one sibling had advanced clinical disease, whereas the other sibling was in good clinical condition. Three in this latter group had no clinically apparent Pseudomonas bronchitis. In all cases, the average responses to Pseudomonas isolated from each sibling pair were lower in the sibling with advanced clinical disease. This difference was not observed in the responses to Staphylococcus. Normal plasma or plasma from patients with CF in good clinical condition does not restore the responses in patients with advanced clinical disease. However, plasma from patients with low or no responses to Pseudomonas inhibits the responses of responding siblings. A progressive specific lymphocyte unresponsiveness to Pseudomonas may play an important role in the increasing destructiveness of chronic pulmonary Pseudomonas infection in cystic fibrosis.

Effect of viral and bacterial pneumonias on cell-mediated immunity in humans

Cell-mediated immunity (CMI) was assessed during infection and after convalescence in 12 patients with influenza pneumonia and 10 patients with bacterial pneumonia. The patients with influenza pneumonia had a marked impairment of skin test reactivity, and their lymphocytes showed a diminished response to phytohemagglutinin and streptokinase-streptodornase stimulation in vitro. Suppression of CMI was related to the severity of the pneumonia. Patients with bacterial pneumonia showed as great a suppression of the response to phytohemagglutinin and streptokinase-streptodornase as the patients with viral pneumonia. All parameters of CMI returned to normal in both groups after convalescence. The depression of CMI could not be related to a decrease in the number of thymus-derived lymphocytes or to serum-suppressive factors in these patients.

[Etiology of acute suppurative destructive pneumonias in children]

Clinical, immunological and bacteriological studies were carried out in 63 children with the so-called staphylococcus destruction of the lungs. It was shown that in some of the cases destructive process in the lungs, along with the pathogenic staphylococcus, could be caused by the Gram negative bacteria (Proteus, Bac. pyocyaneus, etc.). It was found that in children of different age groups the titre of antistaphylococcus antibodies up to 0.5 AU/ml was normal and pointed to the absence of any inflammatory disease of staphylococcus etiology; a titre of 2 AU/ml - and overcould be considered as diagnostic. In connection with bacterial poly-etiology of acute destruction of the lungs in children it is suggested that it should be designated as "acute purulent destructive pneumonia". The importance of immuno-bacteriological studies in children with diseases with the mentioned pathology is emphasized; these examinations permit to choose proper complex therapy.

Pulmonary alveolar macrophage. Defender against bacterial infection of the lung

The rate of ingestion of inhaled bacteria by pulmonary alveolar macrophages is an important determinant of host defense. This parameter was investigated by infecting rats with finely dispersed aerosols bearing Staphylococcus aureus in high concentrations (about 10(s) bacteria/ft(3)/min). These aerosols deposited more than 10(6) bacteria/murine lung. At 0, 2(1/2), and 5 h after infection, bacterial clearance rates were measured in the left lung, and the intracellular or extracellular location of 100 bacteria was determined histologically in the right lung (perfused in situ). The clearance rates at 2(1/2) and 5 h were 44.5% and 76.9%, respectively. The percentages of intracellular bacteria were: 0 h, 54.8%; 2(1/2) h, 87.1%: 5 h, 91.9%. When rats were exposed for 4 h to 2.5 ppm of ozone (O(3)), bacterial clearance did not occur - 15.3%, although 78.7% of the bacteria were intracellular. Clumps of more than 10 bacteria-usually intracellular-were also present. These experiments demonstrate that phagocytic ingestion is an exceedingly rapid process, that in this experimental model the inactivation of inhaled staphylococci results almost entirely from phagocytosis, and that ozone-induced reductions in bacterial clearance are due to severe impairment of intrapulmonary killing mechanisms and minor impairment of bacterial ingestion.

Immunoglobulin levels in pneumonia

Serum immunoglobulin levels were measured by radial immunodiffusion in thirty patients with pneumonia and in thirty healthy controls. In pneumonia the mean IgG level increased during the course of the illness. During convalescence the mean IgM and IgG levels were higher in patients than in controls. The results of immunoglobulin estimations were correlated with the results of aetiological investigations. Patients with M. pneumoniae infections showed a significant rise in IgM concentration which may be specific for respiratory infections associated with this organism.