Who has defective cell-mediated immunity (CMI)?

From the Guidelines

Individuals with defective cell-mediated immunity include those with primary immunodeficiency disorders like Severe Combined Immunodeficiency (SCID), DiGeorge syndrome, and Wiskott-Aldrich syndrome, as well as those with acquired conditions such as HIV/AIDS, certain cancers, and patients undergoing immunosuppressive therapy. These conditions can lead to impaired T lymphocyte function, making individuals susceptible to infections from intracellular pathogens including viruses, fungi, mycobacteria, and certain parasites. According to the study by 1, increased susceptibility to opportunistic infections among acquired immunodeficiency syndrome (AIDS) patients is due to defective cell-mediated immunity.

Key Conditions Associated with Defective Cell-Mediated Immunity

• Primary immunodeficiency disorders: SCID, DiGeorge syndrome, Wiskott-Aldrich syndrome
• Acquired conditions: HIV/AIDS, certain cancers (lymphomas and leukemias), immunosuppressive therapy
• Malnutrition: particularly protein deficiency

Pathogens Affecting Individuals with Defective Cell-Mediated Immunity

• Viruses: herpes, cytomegalovirus
• Fungi: Candida, Aspergillus, Pneumocystis jirovecii
• Mycobacteria: tuberculosis
• Parasites: Toxoplasma

Importance of T Lymphocytes in Cell-Mediated Immunity

T lymphocytes play a crucial role in recognizing and destroying infected cells directly or coordinating immune responses through cytokine production. When this system is compromised, the body cannot effectively eliminate pathogens, leading to severe, recurrent, or unusual infections that can be life-threatening, as noted in studies such as 1 and 1.

Clinical Presentations and Diagnostic Approaches

The clinical presentation of defective cell-mediated immunity can vary widely, including recurrent severe infections, opportunistic infections, and autoimmune manifestations. Diagnostic approaches often involve a combination of laboratory tests to assess immune function, including measurements of immunoglobulin levels, vaccine responses, and B cell and T cell counts, as outlined in studies like 1 and 1.

From the Research

Defective Cell Mediated Immunity

People living with HIV (PWH) have defective cell-mediated immunity, which makes them susceptible to opportunistic infections such as Pneumocystis jirovecii pneumonia (PCP) 2, 3, 4, 5.

• Key factors that contribute to defective cell-mediated immunity in PWH include:
  • Low CD4 cell count 4, 5
  • Impaired function of dendritic cells, macrophages, and CD4+ T cells 3
  • Opportunistic infections such as PCP, Toxoplasma gondii, Cryptococcus, and Mycobacterium avium complex (MAC) infection 3

Populations at Risk

Certain populations are at a higher risk of developing defective cell-mediated immunity, including:

• People with HIV/AIDS, particularly those with low CD4 counts 2, 4, 5
• Individuals with acute kidney injury and chronic kidney disease, such as HIV-associated nephropathy (HIVAN) 3
• Patients with a history of opportunistic infections, such as PCP 2, 4, 5

Treatment and Prophylaxis

Treatment and prophylaxis options for PCP in PWH include:

• Trimethoprim-sulfamethoxazole (TMP-SMX) as the first-line agent for treatment and prophylaxis 2, 4, 5
• Alternative regimens, such as dapsone-based regimens, aerosolized pentamidine, and atovaquone 2, 4
• Antiretroviral therapy (ART) to improve immune function and reduce the risk of opportunistic infections 3, 5