ABSTRACT
Sequential immunization with mycobacterial antigen Ag85B-expressing DNA and Mycobacterium bovis bacille Calmette-Guerin (BCG) was more effective than BCG immunization in protecting against Mycobacterium tuberculosis infection. Depletion of the CD8(+) T cells in the immunized mice impaired protection in their spleens, indicating that this improved efficacy was partially mediated by CD8(+) T cells.
Subject(s)
Acyltransferases , Bacterial Proteins/immunology , Immunization, Secondary , Mycobacterium bovis/immunology , Tuberculosis/prevention & control , Vaccines, DNA/immunology , Animals , Antigens, Bacterial/administration & dosage , Antigens, Bacterial/immunology , Bacterial Proteins/administration & dosage , Mice , Mice, Inbred C57BL , Mycobacterium tuberculosis/immunology , Tuberculosis/immunology , Vaccines, DNA/administration & dosageABSTRACT
The FcR family contains multiple receptors for Igs, of which the most distantly related ( approximately 20%) is the IgA receptor (human Fc alpha R), being more homologous ( approximately 35%) to another family of killer-inhibitory receptor-related immunoreceptors with a 19q13.4 chromosomal location in humans. This study of the Fc alpha R demonstrated that, like several IgG receptors, Fc alpha R is a low affinity receptor for Ab (Ka approximately 106 M-1). Rapid dissociation of the rsFc alpha R:IgA complex (t1/2 approximately 25 s) suggests that monomer IgA would bind transiently to cellular Fc alpha Rs, while IgA immune complexes could bind avidly. Mutagenesis of histidyl 85 and arginyl 82, in the FG loop of domain 1, demonstrated that these residues were essential for the IgA-binding activity of Fc alpha R, while arginyl 87 makes a minor contribution to the binding activity of the receptor. This site is unusual among the Fc receptors (Fc gamma RII, Fc gamma RIII, and Fc epsilon RI), in which the ligand binding site is in domain 2 rather than domain 1, but like Fc alpha R, the FG loop comprises part of the ligand binding site. The putative F and G strands flanking the Fc alpha R ligand binding site are highly homologous in the other killer-inhibitory receptor-related immunoreceptors, suggesting they comprise a conserved structural element on which divergent FG loops are presented and participate in the specific ligand interactions of each of these receptors.
