How do immune deficiency disorders affect the body’s ability to resist infections?

Immune deficiency disorders impair the body’s ability to resist infections by causing defects in key components of the immune system, such as lymphocytes, antibodies, phagocytes, and complement proteins. When these mechanisms are compromised, the body cannot effectively identify, attack, or remember pathogens, leaving the individual susceptible to infections that a healthy immune system would typically neutralize.4123

These disorders can be inherited or acquired, and they undermine the immune response in various ways. For example, some defects prevent B lymphocytes from producing antibodies, while others stop phagocytes from digesting microbes. In severe cases, such as severe combined immunodeficiency (SCID), both humoral and cell-mediated immune responses are disrupted.4125

Acquired conditions like AIDS destroy specific cells, such as helper T cells, which leaves the body vulnerable to opportunistic pathogens that are usually harmless. Without medical intervention—such as immunoglobulins or bone marrow transplant—these individuals remain unable to mount an effective defense against disease.12