American Board of Internal Medicine (ABIM) Certification Practice Exam

What type of cell is often found in dense lymphoplasmacytic infiltrate related to IgG4-related disease?

1. CD8-positive T cells

2. CD4-positive T cells

3. B cells

4. Natural killer cells

The correct answer is: CD4-positive T cells

In the context of IgG4-related disease, a dense lymphoplasmacytic infiltrate is characteristic of this condition. The primary immune cells involved in this infiltrate are often CD4-positive T cells. These T cells play a crucial role in orchestrating the immune response and are involved in promoting B cell function, including the production of IgG4 antibodies. IgG4-related disease is known for its unique immunological profile, where a substantial buildup of IgG4-positive plasma cells occurs, and this is influenced by CD4-positive T cells that support this differentiation and activation of B cells. The presence of these T helper cells is essential as they facilitate the humoral immune response, and their proliferation contributes significantly to the dense infiltrate seen in biopsy specimens from patients with the disease. Other cell types present in an immune response, such as CD8-positive T cells and natural killer cells, typically play roles in cellular immunity and the direct killing of infected or neoplastic cells, rather than in the maintenance of the lymphoplasmacytic environment seen in IgG4-related conditions. B cells do contribute to the immunological landscape by producing antibodies but are more regulated by the CD4-positive T cells and do not define the nature of the dense infiltrate in