Adaptive Immunity  Response occurs within days of the infection  Highly specific  Highly diverse  Memory component  Major cell types involved: T cells, B cells and antigen presenting cells

Antigens and Antibodies (CH4)  Antigen – any substance that binds specifically to an antibody or a T cell receptor (TCR).  Antibody- a protein (immunoglobulin) that recognizes a specific region (component) of an antigen. Naïve B cells – membrane-bound Activated B cells (plasma cells) – soluble (have been secreted)  Immunogen- a substance capable of eliciting an immune response.

Epitope  Epitope – portion of an antigen that reacts with an antibody or T cell receptor (TCR) also known as an antigenic determinant.

Properties of immunogenicity  Foreignness – molecule must be recognized as foreign. tolerance – unresponsiveness to self antigens.

Properties of immunogenicity  Molecular size –correlation between size an immunogenicity. Bigger is better – i.e. macromolecules  Chemical composition/complexity

Properties of immunogenicity  Processing and presentation – important for T cell responses, ability of the antigen to be phagocytosed and processed.  Large  Insoluble  Aggregates

Immunogenicity  Immunogenicity also depends on:  Host factors  Dosage  Route of entry

Recall: Jerne, Talmadge & Burnet – clonal selection theory

Antibody Structure

Antibody-Mediated Effector Functions  Opsonization  Assist/activate complement system  ADCC Marasco and Sui, 2007

Antibody-Mediated Effector Functions  Opsonization – promotion of phyagocytosis of antigens by macrophages and neutrophils. Fc receptor (FcR) Metzger 1994

Antibody-Mediated Effector Functions  Activate and assist complement system

Antibody-Mediated Effector Functions  ADCC – Antibody-dependent cell-mediated cytotoxicity