C4A and tetanus: 1. CBC 2. IgG/A/M/E 3. Lymphocyte subset (CD3, CD4, CD8, CD19/20, and CD16/56) 4. NBT test or DHR test 5. C3, C4, CH50, and AH50 6. Functional antibody response to tetanus, polio, and hepatitis B vaccine 7. Sanger sequencing for BTK, WAS, IL2RG, and CYBB