From: Impact of C4, C4A and C4B gene copy number variation in the susceptibility, phenotype and progression of systemic lupus erythematosus
C4 isotype
Number of copies (mean ± SD)
Controls (n = 301)
SLE (n = 427)
p-value
Total C4
4.17 ± 0.83
3.87 ± 0.96
< 0.001
C4A
2.24 ± 0.73
2.06 ± 0.86
0.001
C4B
1.95 ± 0.71
1.87 ± 0.77
0.192