Human Biology: Bone Marrow and Immune System

Types of Bone Marrow

• Red bone marrow: produces red cells and most white blood cells, typically found at the end of bones (epiphysis) in adults
• Yellow bone marrow: produces some white blood cells, typically found in the canal of long bones in adults, and has a high fat content

Eosinophil Cells

• Involved in fighting parasitic infections and modulating allergic responses

Complement System

• Activates inflammation
• Opsonization (labelling) of pathogens and cells for clearance/destruction
• Direct killing of target cells/microbes by lysis

Myeloid Cells

• Many innate immune cells mature in the bone marrow or shortly after entering circulation
• Maturing cells become myeloid cells

Monocytes and Macrophages

• Monocytes: present in blood circulation (m1 + m2)
• Macrophages: mainly found in tissues, being tissue residents
• M1 Monocytes: fight against infections and foreign invaders
• M2 Monocytes: involved in healing

Phagocytic Cells

• 4 types: monocytes, macrophages, neutrophils, and osteoclasts
• Phagocytic cells consume invading pathogens
• Chemoattractant: attracts phagocytes towards site of infection/injury

MHC 1 and MHC 2

• MHC 1: on all nucleated/infected cells
• MHC 2: only on antigen-presenting cells (APCs)
• MHC is crucial for T cell maturation and function

CD4 Proteins and CD8 Cells

• CD4: recognises antigens presented by APCs
• CD4 + MHC 2
• CD8: recognises antigens on the surface of infected cells
• CD8 + MHC I

B Cell Maturation

• Maturation of B cells occurs in lymph nodes

T Cell Activation

• After T cell activation by APCs, Th cells (CD4 + MHC 2) are activated, and they, in turn, activate B cells
• B cells mature into plasma cells, which enter the circulation

Innate Immune System vs Adaptive Immune System

• Innate Immune System: present from birth, non-specific defence, rapid response, no memory of previous exposures, includes physical barriers, chemicals, and basic cellular components
• Adaptive Immune System: develops over time, highly specific defence, slower response, memory, involves B cells, T cells, and antibodies, communicates with the innate system for a more specific response

Haematopoiesis

• Haematopoiesis: stem cells and precursor cells develop into protective cells
• Originating in the bone marrow, travel through circulation, and mature throughout the body

Types of Stem Cells

• Totipotent: can generate all cell types needed for a new organism
• Pluripotent: capable of producing nearly all cell types in the three germ layers
• Multipotent: able to produce cells within a closely related family
• Oligopotent: limited to generating a few cell types within the same family
• Unipotent: can produce only one specific cell type

This quiz covers the basics of bone marrow types, their functions, and the role of eosinophil cells in fighting parasitic infections. It also touches on the complement system and its functions.