Cell Recognition and The Immune System

Question 1

How are we able to distinguish our body’s own cells (self) from those that are foreign (non self)?

Answer 1

• both ‘self’ and ‘non self’ cells will have protein molecules on their surface
• these proteins vary hugely in their tertiary structure and other properties which makes it possible for our immune system to tell self and non self cells apart

Question 2

What are antigens?

Answer 2

Proteins which both stimulate an immune response and are targets for the response

Question 3

What are foreign cells?

Answer 3

1. Pathogens - disease causing organisms
2. Abnormal body cells - eg cancerous or pathogen infected cells
3. Toxins - these are poisons, they are molecules not cells. Some toxins are produced by bacteria
4. Cells from other individuals eg organ transplant, blood infusion

Question 4

What are our 6 primary defence mechanisms?

Answer 4

1. Skin - outer layer of epidermis contains of keratinocytes, act as a physical barrier
2. Commensal flora - harmless bacteria which live on skin and compete with pathogenic bacteria, these bacteria can be found in other parts of the body such as intestines
3. Mucous membranes - found in gut, genitals, anus, ears, nose + respiratory passages. Sticky mucus lines the passages and traps pathogens. Epithelial layer contains mucus producing goblet cells
4. Eyes - produce tears, contain antibodies and lysozymes
5. Ears- produces ear wax which traps pathogens, produces lysosomes
6. Vagina - secretions contain lactic acid