Sorted By Test Name - Mayo Medical Laboratories

C1Q
8851
C3
Useful For: Screening for common variable immunodeficiency (CVID) Identifying defects in TACI
and BAFF-R in patients presenting with clinical symptoms and other laboratory features consistent with
CVID Evaluating B cell immune competence by assessing expression of BAFF-R and TACI proteins
Interpretation: BAFF-R is normally expressed on over 95% of B cells, while TACI is expressed on a
smaller subset of B cells (3%-70%) and some activated T cells. Expression on B cells increases with B
cell activation. The lack of TACI or BAFF-R surface expression on B cells is suggestive of a potential
common variable immunodeficiency (CVID)-associated defect, if other features of CVID are present. The
majority of TACI mutations (>95%) preserve protein expression but abrogate protein function, hence the
only way to conclusively establish a TACI mutational defect is to perform genetic testing (TACIF/84388
Transmembrane Activator and CAML Interactor (TACI) Gene, Full Gene Analysis).
Reference Values:
%CD19+TACI+: >3.4%
%CD19+BAFF-R+: >90.2%
Reference values apply to all ages.
Clinical References: 1. Warnatz K, Denz A, Drager R, et al: Severe deficiency of switched memory
B cells (CD27+ IgM-IgD-) in subgroups of patients with common variable immunodeficiency: a new
approach to classify a heterogeneous disease. Blood 2002;99:1544-1551 2. Grimbacher B, Hutloff A,
Schlesier M, et al: Homozygous loss of ICOS is associated with adult-onset common variable
immunodeficiency. Nat Immunol 2003;4(3):261-268 3. Salzer U, Chapel HM, Webster ADB, et al:
Mutations in TNFRSF13B encoding TACI are associated with common variable immunodeficiency in
humans. Nat Genet 2005;37(8):820-828 4. van Zelm M, Reisli I, van der Burg M, et al: An
antibody-deficiency syndrome due to mutations in the CD19 gene. New Engl J Med 2006;354:1901-1912
5. Warnatz K, Salzer U, Gutenberger S, et al: Finally found: human BAFF-R deficiency causes
hypogammaglobulinemia. Clin Immunol 2005;115(Suppl 1):820
Complement C1q, Serum
Clinical Information: The first component of complement (C1) is composed of 3 subunits designated
as C1q, C1r, and C1s. C1q recognizes and binds to immunoglobulin complexed to antigen and initiates
the complement cascade. Congenital deficiencies of any of the early complement components (C1, C2,
C4) results in an inability to clear immune complexes. Inherited deficiency of C1 is rare. Like the more
common C2 deficiency, C1 deficiency is associated with increased incidence of immune complex disease
(systemic lupus erythematosus, polymyositis, glomerulonephritis, and Henoch-Schonlein purpura). Low
C1 levels have also been reported in patients with abnormal immunoglobulin levels (Bruton's and
common variable hypogammaglobulinemia and severe combined immunodeficiency), and this is most
likely due to increased catabolism. The measurement of C1q is an indicator of the amount of C1 present.
Useful For: Assessment of an undetectable total complement (CH[50]) level Diagnosing congenital C1
deficiency Diagnosing acquired deficiency of C1 inhibitor
Interpretation: An undetectable C1q in the presence of an absent CH(50) and normal C2, C3, and C4
suggests a congenital C1 deficiency. A low C1q in combination with a low C1 inhibitor and low C4
suggests an acquired C1 inhibitor deficiency.
Reference Values:
12-22 mg/dL
Clinical References: 1. Frank MM: Complement in the pathophysiology of human disease. N Engl J
Med 1987 June 11;316(24):1525-1530 2. Frank MM: Complement deficiencies. Pediatr Clin North Am
2000 December;47(6):1339-1354 3. Frigas E: Angioedema with acquired deficiency of the C1 inhibitor: a
constellation of syndromes. Mayo Clin Proc 1989 October;64(10):1269-1275
Complement C3, Serum
8174
Current as of January 4, 2013 7:15 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 507