Question 1

The immunoglobulin class that has a dimer form found in mucus, saliva, colostrum, and other body secretions is ______.

Accepted Answer

IgA is the immunoglobulin class that exists as a dimer in secretions such as mucus, saliva, colostrum, and other body fluids, playing a crucial role in mucosal immunity.

Question 2

The molecular fragment on an antigen molecule that a lymphocyte recognizes and responds to is called a/an _______.

Accepted Answer

Epitopes are the specific parts of an antigen molecule that are recognized and bound by antibodies or the receptors on lymphocytes, triggering an immune response.

Question 3

During presentation of APC-bound antigen, macrophages and dendritic cells secrete the cytokine _______, which activates T helper cells.

Accepted Answer

Interleukin-1 (IL-1) is secreted by macrophages and dendritic cells during the presentation of antigen by antigen-presenting cells (APCs) and plays a crucial role in the activation of T helper cells.

Question 4

Which process involves antibodies covering surface receptors on a virus or toxin molecule, thereby disrupting their activity?

Accepted Answer

Neutralization involves antibodies binding to the surface of a virus or toxin, blocking its ability to bind to host cells and thus neutralizing its harmful effects.

Question 5

Which immunoglobulin class/es can ?x complement?

Accepted Answer

IgM and IgG are the immunoglobulin classes that can activate the complement system.

Question 6

Small foreign molecules that are too small by themselves to elicit an immune response are termed ________.

Accepted Answer

Haptens are small molecules that, when combined with larger proteins, can elicit an immune response. By themselves, they are too small to be recognized by the immune system.

Question 7

Which process involves antibodies coating microorganisms in order to facilitate phagocytosis?

Accepted Answer

Opsonization is the process where antibodies coat microorganisms to mark them for phagocytosis by immune cells, making it easier for these cells to recognize and engulf the pathogens.

Question 8

Antigen presenting cells _______.

Accepted Answer

Antigen presenting cells include dendritic cells and macrophages, have the ability to engulf antigens and modify them to be more immunogenic, and present processed antigens on their cell membrane surface to T cells, thus all of the given choices are correct.

Question 9

Antigens that elicit allergic reactions are called _______.

Accepted Answer

Allergens are specifically the antigens that cause allergic reactions. They can trigger an immune response in some individuals, leading to symptoms such as sneezing, itching, and more severe reactions like anaphylaxis.

Question 10

Which process involves a more rapid synthesis and greatly increased titer of antibody when the immune system is subsequently exposed to the same antigen?

Accepted Answer

The anamnestic response, also known as the secondary immune response, occurs when the immune system is exposed to an antigen for the second time, leading to a more rapid synthesis and greatly increased titer of antibody compared to the first exposure. This is a fundamental aspect of the adaptive immune system's memory response.

Question 11

Superantigens are _______.

Accepted Answer

Superantigens are bacterial toxins that have the ability to activate T cells at a rate much higher than typical antigens, leading to a massive immune response.

Question 12

The immunoglobulin class that is the only one capable of crossing the placenta is ______.

Accepted Answer

IgG is the only immunoglobulin class capable of crossing the placenta, providing the fetus with passive immunity by transferring antibodies from the mother to the fetus.

Question 13

All of the following are characteristics of IgM except _______.

Accepted Answer

IgM is a pentamer, not a dimer, which means it consists of five monomers joined together, not two.

Question 14

The immunoglobulin class that has an Fc region that binds to receptors on basophils and mast cells is ______.

Accepted Answer

IgE is the immunoglobulin class that has an Fc region that binds to receptors on basophils and mast cells, playing a crucial role in allergic reactions.

Question 15

The immunoglobulin/s found on the surface of B cells is/are _______.

Accepted Answer

IgM and IgD are the primary immunoglobulins found on the surface of naive B cells, acting as receptors for antigen recognition.

Question 16

Which process involves antibodies cross-linking cells or particles into large aggregates?

Accepted Answer

Agglutination involves antibodies cross-linking cells or particles into large aggregates, which is a mechanism used by the immune system to clump antigens together, making them easier to be phagocytosed by immune cells.

Question 17

Which is incorrect about the Fc region of an immunoglobulin?

Accepted Answer

The Fc region of an immunoglobulin does not form the antigen binding sites; those are formed by the Fab (fragment antigen-binding) regions of the molecule.

Question 18

T cell response to T-dependent antigens requires _______.

Accepted Answer

T cell response to T-dependent antigens involves all the listed mechanisms: typically requiring a protein antigen, binding of the T cell to a class II MHC receptor on a macrophage, binding of the T cell to a site on the antigen, and interleukin-1 activating the T helper cell. These steps are part of the complex process of T cell activation and function in the immune response.

Question 19

Which of the following is not a property of B cells?

Accepted Answer

B cells do not require antigen presentation with MHC proteins for activation. This is a characteristic of T cells, not B cells. B cells can be directly activated by antigens.

Question 20

The most abundant class of antibodies in serum is _______.

Accepted Answer

IgG is the most abundant class of antibodies in serum, making up about 75% of serum antibodies in humans. It plays a significant role in the body's immune response by neutralizing toxins and viruses and by mediating other immune responses.

Quiz 15: Host Defenses Ii: Specific Immunity and Immunization