eans that these people have lower immune system
than normal and are more susceptible to infection. This gene encodes for
the C2 protein which is part of an immune system biochemical pathway called
the complement system. It has been proposed that genetic change in the C2
gene has a way of altering the immune regulation mechanism Alper et al.
(1994).. Disrupting the immune biochemical pathway causes autoimmune diseases.
This deficiency has been proven to be have a multifactorial trait. Studies
have shown that unrelated people with this deficiency show symptoms of lupus
erythematosus and polyarteritis. C2 deficiency is often complicated by immunological
disorders such as systemic lupus erythematosis. C2 deficiency has rarely
been reported in the Japanese population. There was a case that was reported
in the Japanese population that helped prove this disorder is associated
with other deficiencies. It has been associated with C9 deficiency and chronic
idiopathic neutropenia Merralls (1995). C9 deficiency has been found to
appear in 0.086% of the Japanese population who are found to have immune,
viral and infectious diseases Merralls (1995). It has not been proven that
these disorders are linked together, but it is highly suggested that the
C9 deficiency has cause some type of mutation on the C2 gene , showing that
there is a relationship among them Merralls (1995).
In Caucasians C2 deficiency is frequently associated with systemic lupus
erythematosis, vasculitis, ankylosing spondylitis, and diabetes. The frequency
of homozygous C2 deficiency in patients with rheumatologic disease is about
0.2% more common than that in the general U.S. population
On a molecular level C2 deficiency is caused by a mutation in the C2 gene
expression. When this defect has taken place there is no detectable mRNA
formed Johnson et al. (1992). In a person who is heterozygous for this deficiency
there is a reduced amount of C2 mRNA Johnson et al. (1992). There are two
main types of C2 deficiency.
Type I and type II are characterized by different expressions and deletions
of the gene. Type I is characterized by no detectable C2 protein being synthesized.
There is a deletion in the 134 basepair single exon Johnson et al. (1992).
Exons are the part of the gene that are expressed, and the intron are the
part that are cut out. This deletion causes a frame shift in the chromosome.
The result of this shift is the generation of a termination codon, TGA,
16 basepairs downstream from the deletion Johnson et al. (1992). A 28 basepair
deletion is detected in the gene 9 basepairs from the 3-prime end of the
134 basepair exon. Type II has a lower than normal synthesis of the C2 protein
Johnson et al. (1992). There are two mutation detected in this type, they
are on exon 5 and exon 11 Johnson et al. (1992).
In conclusion, C2 deficiency is a disorder cause by a mutation in chromosome
6. This mutation causes impaired immunity against bacterial infection. A
person homozygous for C2 deficiency will have a more sever case of infections
than a person who is heterozygous for this deficiency. This deficiency is
a multifactorial trait that is often associated with other immune deficiencies.
Duby DP. Alper CA,;
Polymorphic Hh genes in the HLA-B© region control natural killer cell
frequency and activity Journal of Experimental medicine, 179 (4):1193-203,
1994 Apr 1.
Johnson, C.A.; Densen, P.; Hurford, R.K., Jr.; Colten, H.R.; Wetse, R.A.;
Type I human complement C2 deficiency: a 28-base pair gene deletion causes
skipping of exon 6 during RNA spicing, 1992.
Merralls, Stephanie.; Complement Deficiencies, 1995.
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