CD4+ T cell activation distinguishes response to anti-PD-L1+anti-CTLA4 therapy from anti-PD-L1 monotherapy

Immunity. 2024 Mar 12;57(3):541-558.e7. doi: 10.1016/j.immuni.2024.02.007. Epub 2024 Mar 4.


Cancer patients often receive a combination of antibodies targeting programmed death-ligand 1 (PD-L1) and cytotoxic T lymphocyte antigen-4 (CTLA4). We conducted a window-of-opportunity study in head and neck squamous cell carcinoma (HNSCC) to examine the contribution of anti-CTLA4 to anti-PD-L1 therapy. Single-cell profiling of on- versus pre-treatment biopsies identified T cell expansion as an early response marker. In tumors, anti-PD-L1 triggered the expansion of mostly CD8+ T cells, whereas combination therapy expanded both CD4+ and CD8+ T cells. Such CD4+ T cells exhibited an activated T helper 1 (Th1) phenotype. CD4+ and CD8+ T cells co-localized with and were surrounded by dendritic cells expressing T cell homing factors or antibody-producing plasma cells. T cell receptor tracing suggests that anti-CTLA4, but not anti-PD-L1, triggers the trafficking of CD4+ naive/central-memory T cells from tumor-draining lymph nodes (tdLNs), via blood, to the tumor wherein T cells acquire a Th1 phenotype. Thus, CD4+ T cell activation and recruitment from tdLNs are hallmarks of early response to anti-PD-L1 plus anti-CTLA4 in HNSCC.

Keywords: CD4(+) T helper 1 cells; T cell trafficking; checkpoint blockade; head and neck squamous cell carcinoma; immunotherapy; mechanisms of response; peripheral blood mononuclear cells; single-cell omics; tumor microenvironment; tumor-draining lymph node.

MeSH terms

  • B7-H1 Antigen / genetics
  • CD4-Positive T-Lymphocytes
  • CD8-Positive T-Lymphocytes*
  • CTLA-4 Antigen
  • Head and Neck Neoplasms* / drug therapy
  • Humans
  • Squamous Cell Carcinoma of Head and Neck
  • Tumor Microenvironment


  • B7-H1 Antigen
  • CTLA-4 Antigen
  • CTLA4 protein, human