Lymphocytes can be divided into large lymphocytes and small lymphocytes according to the size of their diameter. Large lymphocytes account for 10% of the whole lymphocytes and small lymphocytes account for 90% of the whole lymphocytes. lymphocytes can be further divided into two categories, T lymphocytes and B lymphocytes, according to the process of development, different markings and functions on the cell surface, and different roles in the process of immune response. t lymphocytes account for 80% of the whole lymphocytes and are mainly involved in cellular immunity, B lymphocytes account for 20% of the whole lymphocytes and are mainly related to humoral immunity and promote antibody production by plasma cells. Therefore, lymphocytes are divided into large lymphocytes and small lymphocytes according to their size, and T lymphocytes and B lymphocytes according to their mechanism of action.