Final answer:
Noncovalent bonds are formed at antigen binding sites, where the variable regions of antibodies and the receptors on T-cells recognize and bind to target antigens in a lock and key manner, using complementary charges and shapes. T-cell interactions also involve Major Histocompatibility Complex (MHC) molecules presenting antigens to T-cell receptors.
Step-by-step explanation:
The bonds formed at antigen binding sites between antigens and T-cells/antibodies are primarily noncovalent interactions. These include hydrogen bonds, electrostatic interactions, van der Waals forces, and hydrophobic interactions. The antigen-binding site on an antibody is formed within the variable regions, which have unique patterns of amino acids that can only bind to target antigens with a molecular sequence that provides complementary charges and shapes. It's important to understand that the specific recognition process resembles a lock and key model, where the receptor on the T-cell or antibody fits precisely with the antigen's structure.
In terms of T-cell interactions, antigen-presenting cells (APCs) will process an antigen and present it on their surface using Major Histocompatibility Complex (MHC) molecules. T-cell receptors (TCRs) recognize and bind to the peptide-MHC complex using similar noncovalent bonds. Helper T cells aid in the production of antibodies by B cells in response to protein antigens, also known as T-dependent antigens, while some B cells can be activated without T cell assistance by T-independent antigens, such as repeated carbohydrate motifs on bacteria.