The Immune System

The immune system Infectious diseases: diseases that can be spread by contact with infected people, animals, water or food Pathogen: an organism or substance that can cause a disease

The immune system Immune system: body system that defends against pathogens

The first line of defence Skin is a physical barrier - stops pathogens from entering the body Sweat & oils on skin are slightly acidic Gastric juices in the stomach can destroy some pathogens Mucus & cilia in the nose stop pathogens from entering the respiratory system

Unfortunately, pathogens still get into our body …

Second line of defence If a pathogen gets past the first line of defence Includes two types of immune response: Innate Immune Response: response you are born with. Acquired Immune Response: specific attack on a pathogen.

Innate Immune Response Quick & general, responds the same to any invader Two steps Flow of fluid into site of infection Causes fever, swelling, and redness in area Swelling and redness = inflammation Increase in the types of white blood cells called phagocytes Phagocytes destroy pathogens.

Acquired immune response A.K.A tertiary defence system Very specific attack on pathogen or antigen Antigen = non-living particle or substance the body cannot recognize All acquired immune responses give you active immunity Active immunity: long lasting protection against a pathogen

Acquired immune response First step in acquired immune response: B cells: recognize antigens present in the body. Produce particles, called antibodies, used to fight antigens.

Acquired immune response Second step in the acquired immune response: Two types of T cells: Helper T cells: recognize antigen or pathogen and activate B cells Killer T cells: recognize & destroy antigen or pathogen without B cells.