What is the Classification of Antigens?

B cells can respond to the surface epitopes of intact antigens but fail to recognize internal epitopes or processed antigens.

But T cells respond to small and cleaved peptides (epitopes) that were buried inside the native antigen, if they were presented through MHC class 11 molecules of antigens presenting cells.

With reference to this character antigens are classified as T cell dependent Antigens and T cell independent antigens.

T cell dependent Antigens:

The antigens that require T lymphocytes to induce immune response and antibody production are referred as “T cell dependent antigens”.

Hence T-dependent antigens do not directly stimulate the production of antibody without the help of T cells.

Structurally these antigens are characterized by a few copies of many different antigenic determinants. Proteins are T-dependent antigens.

T cell independent antigens:

The antigens that are capable of inducing antibody production without T cells help are considered as “T cell independent antigens” (Refer Chapter 5 for B cell activation).

The substances of polysaccharide, lipids, and nucleic acids are T cell independent antigens. These antigens are characterized by repetition of the same antigenic determinant.