Humoral Immunity

This is immunity in which antibody plays the most important role. The cells involved are B cells which differentiate into plasma cells which can excrete antibody. B cells need the help of macrophages, T cells, and sometimes complement in order to destroy foreign invaders (Figure 2-2).

Blood banking is concerned with humoral immunity because red cell antigens cause the production of antibodies. Humoral immune responses can be differentiated into primary (1°) and secondary (2°) responses as follows (Figure 2-3):

Primary and Secondary Immune Responses

Types of Humoral Immunity

Humoral immunity can be subdivided into active and passive immunity. In active immunity the person actively makes an antibody after exposure to a foreign antigen. Active immunity can be artificial (e.g., following vaccination with a live or attenuated virus), or natural (e.g., following exposure to a disease-causing organism). In passive immunity a person is given an antibody that has been made by someone else. It can be artificial (e.g., gamma globulin given to people with agammaglobulinemia) or natural (e.g., maternal antibody that has crossed the placenta into the fetus).

Humoral Immunity