The cells of the adaptive immune response - T cell help and cellular immunity Pt. 2

What type of response do type 1 pathogens (Bacteria/Viruses) initiate?

• Promote a cellular response

Cellular Immunity

• Tc cell proliferation

• Increase macrophage activity

• Help B cells produce antibodies

What type of response do type 2 pathogens (Helminths) initiate?

• Favor a humoral response, inducing mast cell production

Humoral Immunity

• B cell proliferation

• Class switching, e.g IgA & IgE

• Increase Ig production

What type of response do type 17 pathogens (bacteria, fungi) initiate?

• Favors an innate response

Innate Response

• Promote neutrophil responses

Why is activation of the T-Cell a complex process?

• Prevents inappropriate immune responses

What happens when a T-cell is activated?

• They are able to interact with B cells and support their expansion

How do cytotoxic T-Cells kill virus-infected cells?

• Can kill repeatedly, unlike neutrophils

• CTLs release cytotoxic granules that contain perforin and granzyme B. Perforin creates pores in the target cell's membrane, allowing granzyme B to enter and activate caspases, which trigger apoptosis.

What are the granules in the cytotoxic T-cells?

• Modified lysosomes that contain effector proteins in an active form

  • Perforin: polymerizes and forms pores on target cell membrane, aiding delivery of granule contents to cytoplasm

  • Granzymes: group of serine proteases, activate apoptosis by switching on capases

  • Granulysin: protein with broad anti-tumour and anti-microbial activity

What do NK cells do?

Natural Killer Cells

• Recognize “stress” receptors on the surface of virus-infected and malignant cells, they can also detect reduced MHC expression

• Can kill infected cells by ADCC, rich in Fc receptor expression

How do we recognize something is dangerous in the body?

• Pattern recognition receptors (PRRs)

  • Pathogen-Associated Molecular Patterns (PAMPs)

  • Damage-Associated Molecular Patterns (DAMPs)

What is antigen-display?

• Antigen presentation is the display of processed fragments to T-cells for recognition by their T cell receptor

Where do B and T cells encounter antigens?

• B and T cells traffic to lymphoid tissue

• Antigens are carried to lymphoid tissues through the lymphatic system

• Antigens interact with B and T cells in the lymphoid tissues

How is an exogenous antigen recognized?

Recognizes antigens from outside cells (like pathogens), presents on MHC class II, and is recognized by CD4+ T helper cells.

• Activation of helper T cells, antibody production by B cells

How is an endogenous antigen recognized?

Recognizes antigens from inside cells (like infected or cancer cells), presents on MHC class I, and is recognized by CD8+ T cells.

• Killing of infected or cancerous cells