Antibody to serum amyloid A.

BACKGROUND

Serum amyloid A (SAA) is elevated in inflammatory states. While antibodies to CRP, the other major acute phase reactant, have been described, to our knowledge, antibodies to SAA have not. This study was therefore undertaken to determine whether antibodies to SAA could be detected in patients and whether these antibodies are associated with any disease, in particular inflammatory states, using CRP as a proxy for inflammation.

METHODS

An ELISA technique was developed for the detection of antibodies to SAA. Specificity was demonstrated by inhibition. Serum from one hundred and thirty-eight patients sent to the Clinical Immunology Laboratory for CRP evaluations were tested for anti-SAA activity. Their charts were reviewed for clinical parameters, in particular for inflammation, to determine association. Patients were also divided into those with normal and elevated levels of CRP, as a proxy for inflammation. As a control we also studied 62 normals.

RESULTS

The mean OD and 3 SD of the 62 normal blood bank donors for anti-SAA was 0.411 +/- 0.577. Thus for the purposes of this study 0.988 was determined as the cutoff between normality and abnormality. Sixty-one normals and 114 patients had "normal" levels. Elevated levels were observed in 24 patients and 1 normal. There was an association between elevated levels and aortic stenosis, deep vein thrombosis, and systemic lupus erythematosus, seizures, stroke, and atrial fibrillation. There was no association between anti-SAA levels and CRP levels.

CONCLUSIONS

These results show that antibodies to SAA develop in some patients. There was some association with inflammatory cardiovascular diseases.