QCE Biology Unit 2 Topic 2 Revision (A+ level)

Adherence factors enhance pathogenesis by enabling pathogens to:

• Evade the host's immune memory cells

• Bind specifically to host cell receptors and resist flushing mechanisms

• Release toxins that kill host cells directly

• Avoid recognition by antibodies

Bacterial invasion factors primarily function to:

• Facilitate host cell entry or tissue penetration

• Neutralise antibodies in circulation

• Generate energy for bacterial motility

• Promote antigen presentation

The presence of a bacterial capsule assists pathogenicity by:

• Increasing nutrient absorption

• Inhibiting phagocytosis by immune cells

• Enhancing toxin release

• Enabling viral replication

Exotoxins differ from endotoxins in that exotoxins:

• Are heat-stable lipopolysaccharides

• Are secreted proteins that act at distant sites

• Are structural components released only upon cell death

• Do not elicit immune responses

The pathogenicity of Streptococcus pneumoniae is greatly reduced when its capsule is removed because:

• It becomes more motile

• It loses the ability to adhere to surfaces

• It becomes more susceptible to phagocytosis

• It produces more toxins

Host cells identify self by expressing:

• A. Toll-like receptors on their membranes

• B. Major histocompatibility complex (MHC) markers

• C. Complement proteins in plasma

• D. Pattern recognition receptors (PRRs)

MHC class I molecules are found on:

• Only antigen-presenting cells

• All nucleated body cells

• Red blood cells only

• T lymphocytes exclusively

The main function of MHC class II molecules is to:

• Present viral peptides to cytotoxic T cells

• Present extracellular antigens to helper T cells

• Produce antibodies against pathogens

• Activate natural killer cells

Pattern recognition receptors (PRRs) in innate immunity detect:

• Host-specific proteins

• Pathogen-associated molecular patterns (PAMPs)

• Complement fragments

• Self-peptides

Failure to distinguish self from non-self can result in:

• Immunodeficiency

• Autoimmune disorders

• Allergic sensitisation

• Apoptosis inhibition