Local immunity to klebsiella pneumoniae in the lungs of mice.

The development of local immunity to Klebsiella pneumoniae in the lower respiratory tract is described. Immunity to intranasal infection is produced by systemic immunization resulting in high titers of circulating antibody. Protection also follows intranasal immunization with glutaraldehyde-killed organisms. Low levels of antibodies develop in serum after intranasal immunization. IgA antibody can be detected in the serum of these mice whereas little IgA antibody is detected in the serum of mice immunized systemically. Both IgA and IgG antibodies can be found in the pulmonary secretions of locally immunized mice. IgA and IgG from these secretions may be used to passively transfer protection when used to opsonize the infecting dose of K. pneumoniae. Protection mediated by IgA is not due to any interaction of IgA with cells present in the lower respiratory tract during infection, but exerts its protective effect in the upper respiratory tract, thereby preventing the spread of bacterial infection to the lower respiratory tract.