Intro to Immunology / Functions of the Immune System

balanced immune system

• under and over active responses

• external threat and internal self threat 

overview of immune response - lines of defence

• first non-specific - mechanical, chemical, reflex

• second non-specific - innate immunity

• third - specific adaptive immunity

primary and secondary lymphoid tissue

• primary - bone marrow and thymus

• secondary - Peyer’s patch, lymph nodes, spleen

lymph node structure

• cortex - macrophages and dendritic cells

• paracortex - macrophages, dendritic cells, T cells

• medulla - plasma cells, B cells

0-4 hour response

• skin and mucosal membranes - barrier

• macrophages secrete cytokines, histamines, prostaglandins, leukotrienes

• complement active

• mast cells - increase permeability of blood vessels, secrete histamines prostaglandins and leukotrienes

4-96 hour response

• neutrophils phagocytose bacteria

• monocytes differentiate into macrophages

• complement active

3-14 day response

• dendritic cells carry antigens to secondary lymphoid tissue

• antigens move to secondary lymphoid tissue through lymphatic system

• dendritic cells present antigen to T cells

• antigen bound to MHC class I present to CD8 cytotoxic T cells

• antigen bound to MHC class II present to CD4 helper T cells

• B cell receptors detect whole antigens

• helped by CD4 helper T cells

• differentiates, clonal expansion into plasma cells - migrates into medulla

1-4 week response

• 1-2 - T cells move from lymph node to site of infection

• 3-4 - plasma cells secrete antibodies and move to site of infection

• bacteria cleared, immunological memory established

• memory cells reside in tissue and lymphoid tissue

phagocytes and antigen presenting cells

• phagocytes - macrophages, monocytes, neutrophils, dendritic cells

• antigen presenting cells - antigen bound to MHC class II, macrophage and dendritic cells

innate response advantages and disadvantages

• first line of immune defence

• active immediately after antigen enters

• can kill or neutralise large number of aggressors

• antigen dependent

• not highly effective

• no immunological memory

adaptive response advantages and disadvantages

• high antigen specificity

• highly effective elimination mechanism to specific antigens

• memory cells prevent reinfection

• few days

• ineffective for new pathogens

• takes time to overcome infection