C4A and amyotrophic lateral sclerosis: To investigate this, we measured the mRNA levels of key components of the complement pathways, which include the classical/lectin (C1qB and C4), alternative (fB) and terminal pathways (C5a and C5aR1), as well as the major complement regulators (CD55 and CD59a) using quantitative real-time PCR and enzyme-linked immunosorbent assay for C5a in TA muscle of TDP-43Q331K mice during disease progression of ALS (3, 10 and 16 months).