What are the characteristics of good antigen?

Good antigens typically possess several key characteristics: they are usually large, complex molecules, such as proteins or polysaccharides, that can be recognized by the immune system. They often have a high degree of variability and can induce a strong immune response. Additionally, good antigens are usually foreign to the host organism, allowing the immune system to distinguish them from self-antigens. Their structure must also be accessible for binding to immune receptors, facilitating the activation of T and B cells.