Immune System Flashcards

Flashcards about the immune system, MHC molecules, and types of immunity.

HLA molecules

Major self-markers that can also present non-self antigens.

Immune System

The system in charge of defending against pathogens and foreign elements.

MHC Molecules (Major Histocompatibility Complex)

Glycoprotein molecules that determine the identity of body cells. Three classes: Class I (A, B, C), Class II (Dp, Do, DR), and Class III.

MHC Class I molecules

Found on the surfaces of all nucleated cells.

MHC Class II molecules

Found on the surfaces of some immune cells.

MHC Class III molecules

Found in blood plasma.

Graft rejection

MHC molecules are the major cause of __.

Autograft

A graft made from an individual to itself.

Isograft

A graft made from an individual to its genetically identical individual (identical twin).

Allograft

A graft made between two genetically different individuals.

Non-self molecules

Virus molecules, bacteria molecules, vaccines, molecules of different blood types, and different MHC.

Cells of the Immune System

White blood cells or leukocytes that originate from bone marrow stem cells.

Myeloid cells

Originate from myeloid stem cells.

Lymphoid cells

Originate from lymphoid stem cells.

Granulocytes

Have multi-lobed nuclei and granulated cytoplasm.

B Lymphocytes

Have membrane antibody receptors.

T4 Lymphocytes

Have CD4 receptors.

T8 Lymphocytes

Have CD8 receptors.

Organs of the Immune System (Lymphoid Organs)

Primary and secondary lymphoid organs

Primary Lymphoid Organs

Site of production of all leukocytes and maturation of lymphocytes.

Secondary Lymphoid Organs

Site of interaction between the leukocytes and the antigens during the induction of immunity.

Spleen

Site of interaction of leukocytes with antigens carried by the blood.

Lymph Nodes

Sites of the interaction of the lymphocytes with the antigens carried by the lymph.

B and T Lymphocytes

Able to detect in a specific manner the presence of foreign elements.

B Lymphocytes

Recognize free or cellular antigens using membrane antibody receptors.

Antibody

A protein made of four peptide chains: two light chains (L) and two heavy chains (H).

Epitope

The part of an antigen to which the variable region of an antibody binds; also called antigenic determinant.

TCR (T Cell Receptor)

Special membrane receptors on T cells.

TCR of T8

Double specific for HLA class I and non self peptide recognition.

TCR of T4

Double specific for HLA class II and non self peptide recognition.

TCR of T4

Specific for HLA-II non self peptide complex, carried by some immune cells.

Maturation of B Lymphocytes

Process by which self-reactive B lymphocytes are eliminated by the bone marrow.

Body Natural Barriers

Natural defenses against infection, including skin, mucous membranes, and secretions.

Cytokines

Chemical substances released by white blood cells that induce inflammation.

Diapedesis

The migration of white blood cells to the inflammation site.

Macrophages

Attack and eliminate microbes by phagocytosis.

Phagocytosis

Done in three steps: Adhesion, Absorption, and Digestion.

Specific Immunity

An immunity that protects only against the same type of bacteria.

Induction Phase of Immune Response

The phase where the antigen presenting cell waits for the T4 cell with a complementary TCR.

Clonal Selection

The exclusive activation of the T4 specific for the antigen

Humoral Immune Response

Specific BL that recognizes is activated by IL-4 secreted by activated T4 (TH) cells.

Cell Mediated Immune Response

Specific T8 (TC) that recognizes the APC is activated by IL-2 secreted by activated T4 (TH) cells.

Specific Humoral Immune Response

Characterized by the presence in the plasma of specific antibodies.

Specific Cell Mediated Immune Response

Characterized by the presence of Tc lymphocytes that kill cells infected by a virus or an intracellular bacterium.

Cytotoxic T cell

Recognizes the target cell by double recognition and binds by its TCR on HLA-I non-self-peptide complex on its surface.

Neutralization of toxicity

The toxins harm the target cells by binding on specific membrane receptors. When the antibodies bind on the toxins by their variable regions, they cover their site of attachment to the target cells and prevent the toxin from harming them

The opsonization

The antibodies create molecular bridges between the antigen and the phagocyte to facilitate the adherence.

The activation of the complement

After binding C1 components on bacteria antigens, the complex creates membrane attack complexes on the surface of the bacteria and perforates them. This leads to bacteria death.

Immune memory

Memory cells induce a secondary immune response that is faster, more amplified and more persistent than the primary immune response.

Vaccination

Consists of injecting attenuated microbes or attenuated toxins (toxoid) in the body. This injection induces an immune memory that is able to protect the body from the possible subsequent infections.

Serotherapy

Consists of injecting specific antibody molecules to neutralize some microbes or toxins (snake venom) that might enter or have entered to the body.

Immunotherapy

Consists in taking immune cells (Tc cells) that are defending cancer in the body and cultured it in vitro then injected to the patient in order to speed up the elimination of the cancer.

Diagnostic applications of the antibodies.

Antibodies are used in order to test whether an individual is infected or not by a microbe, for example, agglutination.

ELISA tests

Add substrate measure color to test antibodies specific to an intruder (HIV, Hepatitis), it is more sensitive than agglutination test and immunodiffusion in gel.