**2. Basic transplant immunology**

Immune protection against foreign antigens in humans relies on a coordinated response of both innate and adaptive immune system [1]. The innate system, comprising of anatomical barriers (e.g. skin), phagocytic cells (e.g. macrophages), and soluble compounds (e.g. comple‐ ments and interferons [IFN]) provide an efficient initial defence against foreign antigens such as donor antigens in solid organ transplantation but this response lacks specificity. In contrast, subsequent adaptive immune response has the ability to create a large diversity of antigenspecific responses upon antigenic challenge to the host, with the development of immunolog‐ ical memory consequent on subsequent exposure to the same antigen. This response involves predominantly lymphocytes and antibodies, and is characteristically more intense, leading to a more rapid elimination of the foreign antigen (Figure 1).

**The ability of dendritic cells to coordinate innate and adaptive immune system.** Upon exposure to foreign anti‐ gens, dendritic cells secrete pro-inflammatory cytokines ± cell-cell contact, activate effector cells including natural kill‐ er cells and macrophages (innate immunity). Immature dendritic cells capture and process antigens for presentation to T cells via major histocompatibility complexes. DC undergo maturation and migrate to secondary lymphoid tissues (enhanced by inflammatory cytokines produced by natural killer cells and CD40 ligand expressed by activated T cells). Mature dendritic cells drive the expansion of antigen-specific, major histocompatibility complex-restricted T and B cell responses and the development of immunologic memory (adaptive immunity).

**Figure 1.** Innate and adaptive immune response to foreign antigens.
