Functional interaction between human T-cell protein CD4 and the major histocompatibility complex HLA-DR antigen

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Mature T cells differentiate into CD4+ (helper) and CD8+ (cytotoxic/suppressor) subsets.
• T-cell receptor (TCR) recognition is tightly linked to interactions with major histocompatibility complex (MHC) molecules.
• CD4+ T cells interact with class II MHC, while CD8+ T cells interact with class I MHC.

Purpose of the Study:

• To investigate the direct binding interaction between CD4 molecules and class II MHC.
• To overcome experimental challenges in studying CD4:class II MHC interactions.
• To determine if CD4:class II MHC binding augments T-cell activation.

Main Methods:

• Developed a xenogeneic system using transfected murine T-cell hybridomas and target cell lines.
• Transfected human CD4 cDNA into a murine CD4-, CD8- T-cell hybridoma (3DT-52.5.8) recognizing H-2Dd.
• Co-transfected P815 target cells with human class II HLA-DR alpha, beta, and invariant chain cDNAs.

Main Results:

• Co-culture of parental cell lines showed a low baseline response.
• Co-culture of CD4+ transfected T cells with HLA-DR+ transfected target cells yielded a substantial increase in T-cell response.
• This augmented response strongly suggests direct CD4:HLA-DR binding.

Conclusions:

• The study provides strong evidence for CD4 binding to human class II MHC molecules (HLA-DR).
• This CD4:HLA-DR interaction significantly augments T-cell activation.
• The findings validate the proposed model of accessory molecule binding to MHC for T-cell recognition.