Form and function for T cells in health and disease

Understanding the complexity of T cell subsets and their role in disease has been a continuing effort. In 2019, the field saw a number of important advances in identifying new T cell subsets and functional states associated with immunopathology, described molecular mechanisms involved in T cell dysregulation in infection and cancer, and provided insight into what defines a healthy T cell state.

Key advances

• Different types of T follicular helper (T_FH) cell subtypes were identified with specific roles in allergic diseases and anaphylaxis and in promoting recurrent infections.

• CD4⁺ tissue-resident memory T cells are generated from effector cells infiltrating intestines and can mediate direct roles in inflammatory bowel disease.

• The TOX and related TOX2 transcription factors direct a functional programme of exhaustion in CD8⁺ effector T cells and T_FH cell differentiation and promote BCL-6 expression in CD4⁺ T cells.

• CD4⁺ T cell help is required for optimal T cell-mediated immunotherapy in cancer to counteract T cell exhaustion.

• Form and function for T cells can be resolved by single-cell transcriptome profiling, providing context for human T cell functional states in diseases.