Cellular immune response to Klebsiella pneumoniae antigens in patients with HLA-B27+ ankylosing spondylitis

Objective. To study the reactivity of peripheral blood mononuclear cells (PBMC) of patients with ankylosing spondylitis (AS) and rheumatoid arthritis (RA) and healthy controls to Klebsiella pneumoniae antigens and to the GroEL- like proteins from K. pneumoniae (HSP60Kp) and Mycobacterium leprae recombinant heat shock protein 65 (rHSP65Ml). Methods. PBMC of 13 patients with AS and 9 with RA and 10 controls were stimulated in vitro by heat shock induced K. pneumoniae antigens in a cell blot assay, by insolubilized HSP60Kp, by cytosolic proteins (CP) from K. pneumoniae cultivated at 37°C or 45°C, by soluble HSP60Kp, or by rHSP65Ml. Results. In the cell blot assay 7/13 AS and 3/9 RA patients responded to fraction 4, which contains mainly HSP60Kp, and no controls responded (AS vs controls: p = 0.007). The response to the insolubilized HSP60Kp was positive in 6/13 AS patients but negative in RA patients and controls (p = 0.004). The response to CP(45°c) was positive in 7/13 AS, in 2/9 RA, and no controls (AS vs controls: p < 0.015). Response to the soluble HSP60Kp was found in 7/13 AS and 5/9 RA patients, but no controls (AS vs controls: p = 0.0075). Response to rHSP65Ml was positive in 3/13 AS, 7/9 RA patients, and 1/10 controls (AS vs RA: p = 0.027; RA vs controls: p = 0.005; AS vs controls: nonsignificant). Conclusion. In PBMC of the majority of patients with AS and in some with RA, but not in healthy controls, there are cells that proliferate in the presence of HSP60 of K. pneumoniae.