ABSTRACT
Antigen initiates the immune response via presentation of its peptides by antigen-presenting cells (dendritic cells and macrophages) to antigen-specific Th cells. Th cells then help B cells produce antibody, or CTLs develop. A number of factors influence the magnitude and quality of an immune response. These include nature of the antigen, maturity of the immune system (age of host), route of immunization with the antigen, and dose and persistence. Removal of the antigen stops the specific immune response.
