Adaptive Immunity

Vaccine

a medical treatment typically containing antigens or attenuated pathogens designed to stimulate a person’s adaptive immune system to create immunity to a pathogen without actually causing disease.

Subunit vaccine

contains part of pathogen

Whole Pathogen Vaccine

contain a whole pathogen

Nucleic acid vaccine

contain genetic information to produce antigen

Whole pathogen vaccine; Inactivated Vaccines

contain bacteria/viruses that have been killer/altered and cannot reproduce.

Whole pathogen vaccine: Live attenuated vaccine

contain bacteria/viruses that have been weakened.

Subunit Vaccine: Recombinant protein vaccine:

Genetically modified harmless yeast/bacteria so they express antigen

Subunit vaccines: Toxoid Vaccines

Inactivated toxin (toxins are released by some bacteria, causing disease)

Nucleic acid vaccines: RNA Vaccines

RNA inside lipid membrane, translated into antigens

Nucleic Acid Vaccines: DNA Vaccine

→contains DNA which produces antigen

Compare and contrast innate to adaptive immunity

• Innate immunity is:

  • Non-specific: responds the same way regardless of the pathogen

  • Non-adaptive: does not change upon repeat exposures

  • Immediate: responds instantly

• Adaptive immunity is

  • Specific: response depending on the pathogen

  • Adaptive: becomes more efficient upon repeat exposure

  • Delayed: has a response period

Outline the steps involved in antigen presentation (APC)

• Antigen presenting cells (APC) engulf and digest a pathogen, presenting its enzymatically degraded proteins as antigens on their MHC II markers.

• The APC migrates to lymph nodes.

• The APC then presents the antigen to T helper cells until a T helper cell with specific complementary T cell receptors is encountered. The T helper is selected, stimulating the release of interleukins, promoting clonal expansion.

Why is the adaptive immune response specific?

There is a unique set of T cell receptors on every T Helper Cell, facilitating the specificity of the adaptive immune system.

Cell mediated response

• Antigen presenting cells carrying a target antigen on their MHC class 2 markers bind to a complementary naïve T cells cell receptor, triggering the release of cytokines.

• The naïve T cell is activated and undergoes clonal expansion and differentiation into Th and Tc cells.

• Th cells regulate the action of other immune cells whilst Tc cells will travel to the area of infection, bind to affected cells displaying the target antigen and trigger the death of target cells via apoptosis or perforin or granzymes.

Humoral response

• Antigen presenting cells carry a target antigen on the MHC class 2 markers and travel to the lymph nodes where they bind to a complementary naïve T cells cell receptors, triggering the release of cytokines.

• The activated Th cell then undergoes clonal expansion and differentiation into Th and Tc cells. The Th cell then activates a complementary naïve B cell which undergoes clonal expansion and differentiation into plasma and memory B cells.

• Memory B cells remain in the body for future infections whilst plasma B cells produce and release antibodies which can cause agglutination, neutralisation and opsonisation of the pathogen.

compare and contrast cell mediated immunity and humoral immunity

• (1) Both are specific due to clonal selection and thus act against a specific pathogen, &

• (2) both require selected T helper cells to secrete interleukins stimulating clonal expansion and differentiation.

• (1) Cell mediated immunity attacks infected abnormal cells whereas humoral immunity defends against extracellular pathogens &

• (2) Humoral immunity involves the differentiation of naive B cells (into plasma and memory B cells), whereas cell-mediated immunity involves the differentiation of naive T cells (into cytotoxic and memory T cells).

Describe the functions of antibodies: Neutralisation

Antibodies can bind to the sites of pathogens which are used to attack host cells and obstruct them, preventing them from harming the host cells.

Describe the functions of antibodies: Agglutination

→Antibodies bind together with antigens on two separate pathogens, forming antigen-antibody complexes making it easier to phagocytose.

Describe the functions of antibodies:Immobilization

Antibodies can restrict the movement of pathogens around the body through the formation of antigen-antibody complexes.

Describe the functions of antibodies:Opsonization

→Antibodies can bind to the surface of pathogen, marking it for destruction, thus making it easier for phagocytes to phagocytose it.