25.1 : 淋巴和免疫系统简介

Immunity refers to the body's ability to resist infections and diseases. All cells and tissues that provide immunity collectively form the immune system.

Immune responses can be innate — nonspecific defenses present at birth or adaptive — specific responses acquired over time. 

The lymphatic system is a vital component, facilitating the adaptive immune response and some elements of innate immunity.

It comprises four main components: lymph, lymphoid cells, lymphatic vessels, and lymphatic tissues and organs.

Lymph is a clear fluid that transports lymphoid cells and plasma proteins.

Lymphoid cells are a group of immune cells that include lymphocytes, macrophages, and dendritic cells.

Lymphocytes are white blood cells that facilitate the adaptive immune response. Dendritic cells are antigen-presenting cells that activate the lymphocytes. Macrophages are phagocytes primarily involved in the innate immune response.

The lymphatic vessels form a network of vessels that transports lymph throughout the body.

The lymphoid tissues and organs, such as the spleen and thymus, provide the sites for the activation of lymphocytes.