Humoral Immunity: Antibodies and Immune Response

Humoral Immunity

• Physiologic function of humoral immunity is to combat extracellular microorganisms, such as bacteria, viruses, and fungi, through the production of antibodies.

Cell-Mediated Immunity

• T lymphocytes mediate cell-mediated immunity.

Microorganisms and Humoral Immunity

• Humoral immunity combats extracellular microorganisms, such as bacteria, viruses, and fungi.

Defects in Antibody Production

• Defects in antibody production can result in increased susceptibility to infection with extracellular microorganisms, such as bacteria, viruses, and fungi.

Harmful Effects of Antibodies

• Apart from their protective roles, antibodies can be harmful by causing autoimmune diseases, allergic reactions, and serum sickness.

Adaptive Immunity Transfer

• Passive adaptive immunity can be transferred from immunized to naive individuals with serum that contains antibodies.

Functions of Antibodies

• Main functions of antibodies are to neutralize toxins, agonize pathogens, and mark pathogens for destruction.

Antibody Production in Mucosal Organs

• Antibodies are produced in mucosal organs such as the intestine and the airways by plasma cells in the mucosal lymphoid tissues.

Identification of Antibody Parts

• Two enzymes, papain and pepsin, can be used to identify the different functional parts of antibodies.

Affinity of Immunoglobulins

• The term 'affinity' refers to the strength of binding between an immunoglobulin and an antigen.

Isotype Switching

• B lymphocytes differentiate in germinal centers of lymph nodes by isotype switching into plasma cells that secrete IgA, IgG, or IgE.

Isotype Switching Instruction

• Cytokines instruct the B lymphocyte to undergo isotype switching, changing the heavy-chain constant domains to classes of antibodies with new and different effector functions.

Isotype Switching Process

• During isotype switching in B lymphocytes, the excised DNA is circularized and deleted.

Primary Immune Response

• IgM is the principal immunoglobulin of the primary immune response because it is the first antibody produced in response to an initial infection.

Secondary Immune Response

• IgM antibodies are occasionally produced during secondary and later immunologic responses, especially when there is a large amount of antigen present.

Idiotype

• Idiotype refers to the unique antigenic determinants present on the variable regions of an antibody molecule.

Test your knowledge on humoral immunity, including primary and secondary immune responses, antibodies, and class switching. Learn about the physiologic function of humoral immunity in defense against extracellular microbes and microbial toxins.