MCB3020 Week 11: Immunology and Vaccination

Immunity

The active ability of an organism to resist infection, results from the actions of cells that circulate through the blood and lymph systems

Innate immunity

The body's built-in ability to recognize and destroy pathogens or their products, first line of defense

Adaptive immunity

The acquired ability to recognize and destroy a pathogen and its products, activated by exposure of the immune system to the pathogen

Leukocytes

Nucleated white blood cells, includes lymphocytes

Lymphocytes

Specialized leukocytes involved exclusively in the adaptive immune response which includes B cells and T cells

B cells

Type of lymphocyte that originates and matures in the bone marrow, has antibodies for proteins

T cells

Type of lymphocyte that originates in the bone marrow, but matures in the thymus, has TCRs for proteins

Myeloid cells

Cells that work as part of the innate immune response including antigen presenting cells and granulocytes

Antigen presenting cells (APCs)

Myeloid cell type that engulfs, processes, and presents antigens to lymphocytes, includes the two monocytes of macrophages and dendritic cells, as well as B cells

Granulocytes

Myeloid cell type that contains toxins or enzymes that are released to kill target cells, includes neutrophils, basophils, and eosinophils

Invasion

The ability of a pathogen to enter host cells or tissues, multiply, spread, and cause disease with tissue damage triggering the recruitment of phagocytes

Cytokines

When cells are damaged, leukocytes and damaged cells release these chemical mediators that allow communication between WBCs, draws macrophages and neutrophils to the area

Phagocytes

Engulfs and destroys pathogens, includes macrophages, monocytes and neutrophils, moves using amoeboid action and has lysosomes, uses toxic oxygen to kill ingested bacterial cells thru oxidation

Pattern recognition molecules (PRM)

Used by phagocytes to recognize a pathogen, membrane-bound phagocyte proteins recognize PAMPs or pathogen associated molecular patterns

Toll-like receptors (TLRs)

Found on phagocytes, these recognize PAMPs (pathogen associated molecular patterns)

Leukocidins

Produced by some intracellular pathogens, these kill the phagocyte and forms pus, done by infections involving S. pyogenes and S. aureus

Inflammation

Nonspecific reaction to stimuli produced by proteins cytokines and chemokines which isolates and limits tissue damage by destroying damaged cells and pathogens, can result in considerable damage to healthy tissue

Interleukins

Neutrophils are attracted to the site of infection by this kind of cytokine released by the damaged host cell

Septic shock

If inflammation fails to localize the pathogen and the reaction becomes widespread, this condition could follow, more dangerous than the initial infection as it's an uncontrollable fever that has a 30% mortality rate

Cell-mediated immunity

Immunity that leads to the killing of pathogen-infected host cells through recognition of pathogen antigens found on infected host cells

Antibody-mediated/humoral immunity

Immunity that is effective against extracellular pathogens such as bacteria and soluble pathogen products

Antigens

Substances that react with antibodies or TCRs (t cell receptors)

T cell receptor (TCR)

Membrane protein found on T cells

Major histocompatibility complex (MHC)

Functions as antigen-presenting molecules, presents items from inside cells, includes two variants, found on the outside of cells on the membrane

MHC1

MHC protein variant that is found on all nucleated cells, mainly reacts with cytotoxic T cells

MHC2

MHC protein variant that is found only on B lymphocytes (B cells), macrophages, and dendritic cells, mainly reacts with T helper cells

Cytotoxic T cells (CTLs)

T cell variant that kills cells displaying foreign antigens in MHC1

Natural killer cells (NK cells)

Cell that kills targets that lack a specific protein, the lack of normal MHCs result in killing, recognizes the antigen presented by an MHC1 protein on an infected cell that kills antigen-bearing target cells directly

T helper cells

Interacts with peptide-MHC2 complexes on the surface of antigen-presenting cells, acts through cytokines to promote immune reactions

T1 subset

T helper cell type that activates macrophages by secreting cytokines and initiating inflammation

T2 subset

T helper cell type that plays a crucial role in B cell activation and antibody production, does not interact directly with the pathogen but stimulates other cells (B cells)

Antibodies/Immunoglobulins

Protein molecules that interact specifically with antigens, 5 major classes include IgG, IgA, IgM, IgD, and IgE with IgG being the most common one circulating in the body, soluble proteins that are made by B cells in response to exposure of nonself antigens that are part of pathogens or their products

Antigen-binding site

Results from the interaction between heavy and light chains

Antibody production

Antigen-stimulated B cells multiply and differentiate to form antibody-secreting plasma cells and memory cells as the primary antibody response, with memory cells being transformed into antibody-secreting cells over the years as the secondary antibody response

Complement

Group of sequentially interacting proteins that has roles in innate and adaptive immunity, causes lysis of pathogens or marks them for recognition by phagocyte, lyses many gram-negative bacteria

Opsonization

A bacterial cell is more likely to be phagocytized if it has been bound by an antibody, complement binds antibody-antigen complex which increases the likelihood of phagocytosis further

Superantigens

Proteins capable of eliciting a strong response as they activate more T cells than normal, produced by interaction of viruses and bacteria with TCRs, can cause systemic inflammatory reactions

Natural active immunity

Immunity is acquired by an infection that initiates an adaptive immune response

Natural passive immunity

Immunity is acquired thru an antibody transfer across the placenta or in breast milk

Artificial active immunity

Immunity is achieved through exposure to a controlled dose of a harmless antigen to induce the formation of antibodies

Artificial passive immunity

Immunity is achieved through injection of an antiserum derived from an immune individual

Immunization

The process of generating an artificial active immune response by exposure to an antigen or antigen mixture thru a vaccine, most effective when live cells or virus is used

Synthetic peptides

Alternative approach for preparation of immunization that prevents foot and mouth virus

Recombinant-vector vaccines

Alternative approach for preparation of immunization that includes the rabies vaccine

Recombinant-antigen vaccines

Alternative approach for preparation of immunization that includes the hepatitis B vaccine

DNA vaccines

Alternative approach for preparation of immunization that is based on the expression of cloned genes in host cells

Primary antibody response

Activated B cells differentiate into plasma cells that produce soluble antibodies

Secondary antibody response

Subsequent exposure to the same antigen induces memory