Question

Antigens are usually present
A. Inside nucleus
B. On the cell surface
C. Inside cytoplasm
D. On nuclear membrane

Answer 1

Hint: The immune system of the living organism is a dynamic system and it causes protection against a variety of invaders or foreign agents. The immune response is based on the types of infectious agents that have entered the body and in course of infection, it has elevated the defense system. Antigens are toxins or other foreign materials which are capable of induction of immune responses in the body.

Complete answer:
The blood of the humans is made up of red blood corpuscles which carry the respiratory pigment. The surface of the red blood cells contains a specific molecule on their surface known as the antigen and are inherited. The antigens present on the red blood cells are also known as blood group antigens as they are responsible for the blood group system. They are carbohydrates that are attached to the proteins and lipids. The different types of blood groups in humans are due to the presence of two types of antigen which are type A and type B antigens. When a person contains type A antigen, the body produces antibody B and the blood group is A. When type B antigen is present, the antibody produced is antibody A and the blood group is B. Incase, there are no antibodies produced, the blood group will be AB and when both antibodies A and B is produced, The antigens are not present in the blood and the blood group is group O.
The antigens present on the blood cells are the antigen produced by the body and do not produce immune responses. They are identified as inherited molecules present on the surface of the cells of the blood.
Antigen can be described as a molecule or molecular structure of toxin material, pathogenic materials or self-produced chemical and it causes an immune response. The presence of foreign antigens in the body triggers immune responses through a natural process. The antigen can be referred to a structural molecule that is present on the surface of the cells and it binds with the antibody. The antigens bind to the antigen-specific antibodies, T-cell receptor or the B cell antigen receptors. The T-cell and the B cell are cellular components of immunity.
The antigens are made up of proteins, peptides or polysaccharides. In addition to these components, lipids and nucleic acids may also combine to create an antigen complex.

Therefore, the correct option is option B.

Note: Antigen are molecules or structural components that are present on the surface of the cell. When the antigens are inherited and are naturally present on the blood cells or the RBCs do not increase the immune responses by the immune system. The antigens agents when present on the surfaces of the foreign pathogenic toxins can evoke immune responses by activating the antibodies.