Helper T cell immunity in humans with inherited CD4 deficiency

Area of Science:

• Immunology
• Human Genetics

Background:

• CD4+ T cells are crucial for immune responses and regulation.
• The specific function of CD4 protein remains incompletely understood.

Purpose of the Study:

• To investigate the role of CD4 in immune function and host defense.
• To characterize the clinical and immunological features of CD4 deficiency.

Main Methods:

• Studied seven patients from four ancestries with autosomal recessive CD4 deficiency.
• Analyzed CD4 variants, T cell populations (CD4+ and TCRαβ+CD4-CD8-), and their functional responses.
• Assessed immune cell interactions with LCK and HLA class II.

Main Results:

• Patients presented with infections like warts and Whipple's disease, linked to homozygous deleterious CD4 variants.
• All patients lacked CD4+ T cells but showed increased TCRαβ+CD4-CD8- T cells resembling Th cells.
• These compensatory T cells demonstrated intact HLA class II-restricted antigen responses and supported B cell differentiation.

Conclusions:

• Compensatory T cell development allows effective immunity against many pathogens despite CD4 deficiency.
• CD4 is indispensable for protection against human papillomaviruses and Trophyrema whipplei.