Immunity

Definition of immunity

  • Body’s ability to resist/eliminate potentially harmful foreign material

  • Defense, removal of worn out cells, rejection of foreign cells, inappropriate response



Different components of the immune system

  • Cells, tissues, organs, proteins

  • Primary lymphoid organs: bone marrow, thymus

  • Secondary lymphoid organs: spleen, lymph nodes, lymph tissues

  • Vessels, ducts



Primary and secondary lymph organs/tissues

  • Primary lymphoid organs: bone marrow, thymus

  • Secondary lymphoid organs: spleen, lymph nodes, lymph tissues



Origins of immune cells (hematopoiesis)

  • Only plasma cells and memory cells, following exposure, are produced in the secondary lymphoid organs

  • Everyone else originates from hematopoiesis

Myeloid progenated

  • Respond first

  • More general response

  • Innate immunity 

Lymphoid progenated

  • Adaptive immunity 

  • NKs, T cell progenitor (thymus originated)

**dendritic cells originate from both

Thymus

  • Thymus medulla is the site of development + maturation of T lymphocytes

Spleen

  • After being produced, they’re reserved in secondary lymphoid organs

  • B cells are in the basal cell area in the follicles (white = germinal), (red = 

  • T cells are stored in the periarteriolar lymphatic sheaths 

  • Marginal zone = APC, macrophages

Lymph Nodes

MALT - mucosa associated lymphatic tissue (can be bronchial, gut, skin, vulvo associated)



TO KNOW

Types of significance of immune cells

Myeloid Cells

Mononuclear phagocytes

  • Monocytes - 1 nucleus, larger than lymphocytes, agranulocytes (like lymphocytes)

Polymorphonuclear granulocytes

  • Neutrophil, eosinophil, basophil, single nucleus with multiple lobes

  • Lymphocytes are slightly larger

  • Neutrophils -  most abundant, multilobed, are activated to kill

  • Eosinophils - bilobed with reddish granules, increases with allergic rxns

  • Basophils - similar to mast cells in inflammation, dark blue granules, least

  • Mast cells - in response to allergy or parasites



NLMEB  → different amounts (50-70, 20-40, 1-6, 1-3, >1)



Lymphoid Cells

  • Includes T, B cells, NKs, and dendritic 

B cells - from bone marrow, bursa in birds, mature ones recognize immunoglobulin 

  • Which have receptors for Ag

  • Effect cells - plasma cells that secrete Ab, end stage

  • Memory B cells - longer life spans, membrane bound structure

T cells 

  • Recognize specific antigens, 

  • T helper cells - presence of CD4 glycoproteins, secretes cytokine

  • T-cytoxic - expresses CD8 membrane glycoproteins

  • T-regulatory cells - from T helper cells

NKs

  • Mature in bone marrow

  • Early role, MSC class 1 inhibitors cause an apoptotic death



Consequences of the general response 

  • + = pathogen removal, healing, repair, surveillance, memory for the immune system

Immediate - redness, swelling, heat, fever, pus formation

  • - = autoimmune diseases, hypersensitivity, allergies (immunoglobulin E, eosinophils), sepsis, inflammation for a while, transplant rejection



Chronic infection, immunodeficiency, opportunistic infections