Which changes in the cell-mediated response can lead to the development of common variable immunodeficiency (CVID)?

Updated: Feb 23, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
  • Print
Answer

A number of factors and cofactors stimulate Ig secretion from B cells harvested from patients with CVID. These factors include B-cell mitogens, soluble T-cell factors, specific B-cell differentiation factors, the Epstein-Barr virus, interleukin 2 (IL-2), interleukin 4 (IL-4), and interleukin 10 (IL-10). Perhaps the most potent stimulant is the CD40 ligand, which is expressed by activated CD4+ cells. In fact, in 40% of patients with CVID, the CD40 ligand is expressed in low levels on activated T cells. In these patients, decreased IL-2 production after T-cell receptor stimulation is also present.

A common defect is the response to antigens by CD4+ T lymphocytes. After immunization, some patients with CVID have decreased numbers of circulating responsive CD4+ T cells. Other patients have an increased number of CD4+ T cells, but they also have an increased rate of apoptosis of these cells. Signal transduction appears to be the primary defect in these T cells. Rezaei et al report on the meningococcal vaccination response in CVID patients. They suggest it may help define subgroups of patients, which may lead to better monitoring and new therapeutic strategies. [20]

Of all patients with CVID, 25-30% often have increased numbers of CD8+ T cells and a reduced CD4/CD8 ratio (< 1). The cause is an increase in cyclic adenosine monophosphate levels and the increased activation of protein kinase A. On physical examination, patients with this subtype often have splenomegaly and bronchiectasis. In addition, 60% of patients with CVID have a diminished response to T-cell receptor stimulation and expression of receptors for IL-2, IL-4, interleukin 5 (IL-5), and interferon gamma. However, the T-cell receptors show no evidence of abnormality; in fact, genetic findings indicate normal heterogeneity of the genetic rearrangements. Therefore, most patients with CVID can be said to have antibody deficiency secondary to T-cell signaling abnormalities, as well as defective interactions between T and B lymphocytes. Laino et al report that the prevalence of distinct clinical complications of CVID is higher in patients with B- and T-cell abnormalities. [21]

Both the transient and permanent recovery of Ig production has been reported in both patients with HIV and in patients with hepatitis C infection. This finding may indicate that CVID is associated with potentially reversible defects in humoral and/or cellular immunoregulatory factors.

TACI (transmembrane activator and calcium-modulator and cyclophilin ligand interactor) mediates isotype switching in B cells. One series found that 4 of 19 unrelated individuals with CVID and 1 of 16 individuals with IgA deficiency had a missense mutation in 1 allele of TNFRSF13B (encoding TACI). [22] TTACI mutations can result in CVID and IgA deficiency. Four genes have been documented to be mutated in CVID patients: ICOS, TNFRSF13B (encoding TACI), TNFRSF13C (encoding BAFF-R) and CD19. [23] Heterozygous mutations in TNFRSF13B are also associated with CVID, [13] whereas the other 3 genes are recessive. [24, 25] Those with a mutation in the TNFRSF13B gene may require further investigation.

Autosomal dominant CVID has been linked to chromosome 4q. [26] One study supports the existence of a disease-causing gene for autosomal dominant CVID/IgA deficiency on chromosome 4q. Other possible loci for dominant CVID genes are on chromosomes 5p and 16q.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!