Microbiology Rheumatoid factors are immunoglobulins directed against: A The Fc poion of immunoglobulin G (IgG) B The Fc poion of immunoglobulin A (IgA) C The Fc poion of immunoglobulin M (IgM) D The Fc poion of immunoglobulin D (IgD) 💡 Explanation Rheumatoid factors are immunoglobulins directed against: ✓ Correct Answer: A. The Fc poion of immunoglobulin G (IgG)