Which investigation best assesses humoral defects by measuring antibody responses to vaccines?

• A. Hemoglobin determination
• B. Ig level determination and antibody response to vaccines
• C. NBT test
• D. Measurement of chemotaxis

Answer: (B)

Humoral immune defects are best detected by testing the body's ability to produce specific antibodies in response to an antigen. This means assessing both the amount of antibodies circulating in the blood (immunoglobulin levels) and the actual functional response to vaccination. Measuring immunoglobulin levels shows whether there is a quantitative deficiency, but some individuals have normal levels yet cannot mount an adequate antibody response. Evaluating the antibody response after vaccination reveals functional capacity of B cells to generate antigen-specific antibodies and develop memory. Together, these tests directly assess humoral function.

Other tests target different parts of the immune system: measuring hemoglobin assesses blood for anemia; the nitroblue tetrazolium test evaluates neutrophil respiratory burst (phagocyte function); and chemotaxis measures leukocyte movement. While important for other immune problems, they do not characterize humoral antibody production.