Antigens are chemical substances that are capable of triggering an immune response in the host body by initiating antibodies production that helps resist bacterial infections. Depending upon the antigen source, i.e., whether they enter the body from outside or originate within the body, the antigens can be classified into self-antigens and foreign antigens. The foreign antigens include viruses, parasites, bacteria, and many more. The bacterial antigen antigenic determinant portion is recognized by antigen-specific receptors present on T and B cells. These determinants induce a strong immune response and, therefore, are used to generate antibodies for research purposes.