And one more serology paper

 According to

Clin Diagn Lab Immunol. 2003 January

Measurement of Chlamydia pneumoniae-Specific Immunoglobulin A (IgA) Antibodies by the Microimmunofluorescence (MIF) Method: Comparison of Seven Fluorescein-Labeled Anti-Human IgA Conjugates in an In-House MIF Test Using One Commercial MIF and One Enzyme Immunoassay Kit


"...The diagnosis of acute Chlamydia pneumoniae infection is usually based on the demonstration of at least a fourfold increase in immunoglobulin G (IgG) antibody levels in serum samples between the acute phase and the convalescent phase or the presence of IgM antibodies in any serum sample..."

AHA! (for me, at least) -- Dianna's third find on the subject