Biology Quiz: Antigens And B Cells

The correct answer is 5 or five. Antibodies are proteins produced by the immune system in response to foreign substances called antigens. These antibodies are classified into different isotypes or classes based on their structure and function. The five main classes of antibodies are IgG, IgM, IgA, IgD, and IgE. Each class has unique properties and functions that contribute to the overall immune response against pathogens.

There are two isotypes of light chain. This means that there are two different types of light chains that can be found in antibodies - kappa and lambda. These light chains combine with heavy chains to form the structure of an antibody molecule. The presence of two different light chain isotypes allows for diversity and specificity in the immune response.

Somatic hypermutation is a process that occurs after a B cell has encountered an antigen. It is part of affinity maturation, which is the process by which B cells produce antibodies with higher affinity for the antigen. Somatic hypermutation involves a high rate of mutation in the variable regions of the antibody genes, resulting in the production of many different antibodies. This process also involves the complementarity-determining regions (CDR1 and CDR2) of the antibody, which are responsible for binding to the antigen. Therefore, all of the given statements are correct.

Rag-1 and Rag-2 are enzymes involved in somatic recombination. Somatic recombination is a process that occurs during the development of immune cells, where segments of DNA are rearranged to create a diverse repertoire of antibodies and T-cell receptors. Rag-1 and Rag-2 proteins are responsible for recognizing and cleaving DNA at specific sites, allowing for the rearrangement of gene segments. This process plays a crucial role in generating a diverse and functional immune system.

A naive B cell refers to a B cell that has not yet encountered an antigen. It produces two types of antibodies, IgM and IgD. This means that it can produce both IgM and IgD antibodies in response to an antigen. However, it cannot express multiple light chains. Therefore, the correct answers are A and B only.

B cells are a type of white blood cell that produce antibodies. The first immunoglobulins, or antibodies, that a B cell expresses are IgM and IgD. IgM is the first antibody produced during an immune response and is responsible for activating the complement system. IgD is also expressed on the surface of B cells and functions in the activation and differentiation of B cells. IgG, IgA, and IgE are produced later in the immune response.

Antibodies are glycoproteins, meaning they have carbohydrate molecules attached to them. They are composed of two heavy chains and two light chains, which are different types of protein subunits. Antibodies can also be cleaved into different fragments using enzymes such as papain and pepsin. Therefore, all of the given properties (A, B, and C) are true for antibodies.

Immunoglobulin genes are not expressed in germline configuration. They undergo a process called V(D)J recombination, where different gene segments are rearranged to generate a diverse repertoire of antibodies. This recombination occurs during the development of B cells in the bone marrow, leading to the expression of unique immunoglobulin genes in each individual B cell. Therefore, the correct answer is False.

The presence of IgM antibodies indicates a recent infection. IgM is the first antibody produced by the immune system in response to an infection, and its levels rise rapidly during the early stages of an infection. It is typically present in the bloodstream for a short period of time before being replaced by other antibodies such as IgG. Therefore, the transient presence of IgM can be helpful in diagnosing recent infections.