The utilization of receptor protein applicants, for example, Respiratory syncytial virus fusion protein chains A48, Influenza A virus nucleoprotein49,50, and Influenza B virus nucleoprotein51 in the diagnosis of pneumonia is justified because they are synthesized in generally high concentration inside body fluid across all strains and subtypes of these microorganisms; do not change with time; abundantly available either as cell surface receptor and moderately stable to a gentle in vitro handling. This evidence concerns the gene CD177 and pneumonia.