The autoimmune antibodies of rheumatoid factor are directed against which form of abnormal immunoglobulin?

Appeared in: UPUMS Nsg officer-2023

Explanation

Rheumatoid factor (RF) is an autoantibody, meaning it is an antibody that mistakenly attacks the body's own tissues.
Specifically, RF is directed against the Fc (fragment, crystallizable) portion of the body's own Immunoglobulin G (IgG).
While the RF antibody itself is most often of the IgM class, its target is IgG.
The binding of RF (IgM) to IgG forms immune complexes that deposit in the joints, triggering the inflammation and damage characteristic of rheumatoid arthritis.

Option A: This is incorrect because while rheumatoid factor is most commonly an IgM-class antibody, it is directed against IgG, not against itself.
Option C: This is incorrect as IgE is primarily involved in mediating allergic (type I hypersensitivity) reactions and defense against parasitic infections.
Option D: This is incorrect because IgA is the main immunoglobulin in mucosal secretions (e.g., saliva, tears, gut fluid) and provides localized immunity at body entry points.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of rheumatoid arthritis and the function of rheumatoid factor as background academic context rather than a clinical decision trigger.
Testing for rheumatoid factor in the blood is a key part of the diagnostic workup for rheumatoid arthritis. It is included in the 2010 ACR/EULAR classification criteria for RA.
High titers (levels) of RF are often associated with more severe disease, including extra-articular (outside the joint) manifestations like rheumatoid nodules and vasculitis.
It is important for nurses to know that RF is not 100% specific to RA; it can be positive in other autoimmune diseases (like Sjögren's syndrome), chronic infections, and even in a small percentage of healthy older adults.

How to Approach the Question

First, identify the key terms in the question: 'rheumatoid factor' (RF) and 'directed against'. This asks for the target of the RF antibody.
This is a factual recall question about the definition and mechanism of a specific autoantibody in an autoimmune disease.
Recall the basic pathophysiology of rheumatoid arthritis. You need to remember that RF is an antibody that attacks another antibody.
Differentiate between the RF antibody itself and its target. The RF antibody is usually of the IgM class.
Remember that the target of this IgM antibody is the patient's own IgG.
Scan the options and select the one that represents the target of the RF antibody, which is IgG.

Concept Tested & Keywords

Concept Tested: Pathophysiology of rheumatoid arthritis and the function of rheumatoid factor
Stem keywords: rheumatoid factor, autoimmune antibodies, immunoglobulin
Lead-in keywords: directed against
Negative lead-in flag: false

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E6 Medicine Harrison 22e Part 2 p. 683-685

E6 Medicine Davidson Principles Practice 24e p. 1011-1013

Practise the full UPUMS Nsg officer-2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.