Primary immunodeficiency refers to defective immunity arising from inherited or spontaneously acquired gene defects (as opposed to secondary immunodeficiency, caused by external agents), affecting B cells, T cells, combined T/B cells, or phagocytic cells; inheritance patterns include autosomal recessive, autosomal dominant, and X-linked. The specific immune component that is defective determines the characteristic spectrum of opportunistic infections seen (e.g., T-cell defects predispose to intracellular pathogens such as viruses and mycobacteria, while B-cell, phagocyte, and complement defects predispose to extracellular bacteria), making the study of these rare diseases a valuable tool for understanding the function of individual components of the immune system within immunology.
Primary immunodeficiency refers to defective immunity arising from inherited or spontaneously acquired gene defects (as opposed to secondary immunodeficiency, caused by external agents), affecting B …