By: Farnaz Hosseini
Blood and Immunity:
Lecture 3 Innate Immunity
(text book and lecture notes complied) (black-textbook and red- lecture notes
Textbook chpt 23 page 668-675
Review from lecture 2:
• Immunity refers to the immune system capacity to protect individual from disease
by recognizing and eliminating pathogenic (disease generating) agents like
bacteria, virus, parasites, and fungi
• The immune system disposes unneeded components of the body like aging cells,
debris, heals wounds, eliminates mutant cells that can become cancerous
• It also has the ability to reject tissues and cells not identified to self (problem for
• These foreign substances induce the immune system to develop immune
response- a complex series of physiological events accumulates in destroying
• Phagocytes- neutrophils, eosophils, monocytes, macrophages, dendritic cell are
all in this category because they can engulf foreign substances removing them
from the blood
1. Neutrophils are a lot in leukocytes fighting bacterial infections and
elevation in neutrophils In blood is used to determine if the body has an
infection. Neutrophils release cytokines creating inflammation
2. Eosiphils – these defend against parasite by releasing toxic molecules
3. Monocytes- these are phagocytes in blood but they differentiate into
macrophages being 5-10x larger than monocytes and greater activity in
tissue • Lymphocytes – they provide diversity, specificity, memory and ability to
distinguish between self and non self
• 3 major types: B cells (b lymphocytes), T cells and null cells (lack membrane
components characteristic of B and T cells)
• most null cells are large, granular, known as natural killer (NK) ]
• when B cells contact foreign molecules known as antigen they then develop into
molecules known as antigen where than they develop into plasma cells secreting
antibodies called immunoglobulin
• immunoglobulin- these are proteins in plasma and interstitial fluid targeting
specific antigen for destruction
• for example- B cell contacts bacteria aurous , develop into plasma cell secreting
antibodies that only bind to aurous and mark them for destruction
• T cells- these do direct damage to foreign by contacting infected cell, mutant, and
transplanted cells and take several days to develop into an active cytotoxic T cell
• T cells destroy by secreting molecules that form pores in target cells membrane
than succumbs to lysis
• Lysis- this is a process in which I fills with fluids and bursts
MAST CELLS AND DENDRITIC CELLS
• Precursors of mast and dendritic cells are formed in the bone marrow from
hematopoietic stem cells.
• Circulate freely and mature in the tissue.
• Mast cells: found in skin and mucosal epithelial tissue; secrete histamine.
• Dendritic cells: similar to macrophages in their ability to phagocytose or
• All leukocytes develop from hematopoietic cells (blood-forming) stem cells in the
bone marrow. B
• lymphocytes also fully mature in the bone marrow.
T lymphocytes must migrate to the thymus gland before they develop into maturity.
• Central lymphoid tissues: bone marrow and the thymus (as well as the fetal liver)
are sites of lymphocyte maturation.
• Peripheral lymphoid tissue: spleen, lymph nodes, tonsils, adenoids, appendix,
lymph nodules (GI tract),
and regions in the lining of the GI (Peyer’s patches); collections of B cells, T cells, and
• Each peripheral lymphoid tissues contains a dense network of cells hat trap microorganisms and foreign particles.
• B ACTERIA :HAVE THEIR OWN DNA , THEIR MACHIENRY IS DIFFERENT WHILE THE
CHEMICALS IN BACTERIA CAN INHIBIT THEIR ENZYMES WHILE ALLOWING OURS
• V IRUSES-THEY ARE NOT CELLS
• THEY MUST BE IN OUR CELLS TO USE OUR RIBOSOME P erih erallym pho idtisu e
LYMPHOCYTES REACH MATURITY IN CENTRAL LYMPHOID TISSUE AND INTERACT WITH FOREIGN
ANTIGENS IN THE PERIPHERAL LYMPHOID TISSUE
• THESE LYMPHOID TISSUES ARE INTERCONNECTED BY BLOOD VESSELS AND LYMPHOTIC
VESSELS WHICH LYMPHOCYTES CIRCULATE
24.3 – the spleen has the same structure as the lymph node
24.2 – lymphotic vessels (green) – microforeign come inside . They can exist through the
blood or vein
• Spleen collects worn-out erythrocytes from the blood; it is also collecting
bloodborne microorganisms and foreign particles. Microorganisms and particles carried in lymph are trapped by lymph node (where lymphatic
• Macrophage and lymphocyte networks of the spleen and lymph nodes filter
blood and lymph, respectively.
• Tonsils and adenoids trap inhaled particles and microorganisms.
• Appendix, lymph nodules and peyer’s patches trap substances that enter the
body in ingested food or water.
Includes physical barriers, inflammation (a complex series of events causing
accumulation of proteins, fluid, and phagocytic cells in an area of tissue that has been
injured or invaded by microorganisms), interferons (a family
of related proteins that can induce virus resistance to other cells),complement system ( a
group of plasma proteins that act to lyse foreign cells).
1) physical barriers:
• Skin and mucous membranes.
• Skin consists of an outer epidermis and inner dermis. Epidermis consists of
tightly packed epithelial cells and lacks blood vessels.
• Outermost layer is composed of dead cells and keratin.
• Within the dermis are sebaceous glands, which secrete an acidic oily substance,
sebum that inhibits bacterial growth.
• Viscous mucus, which bathes the surfaces of exposed epithelia and can trap
foreign matter and potential pathogens. Have ciliated epithelial cells that line the
• Microbial invasion or damage to tissue triggers a complex series of events that
rapidly lead to inflammation of the affected tissue.
• 5 major events: 1) nearby macrophages engulf debris and foreign matter 2)
nearby capillaries dilate and become more permeable to proteins and fluid 3)
foreign matter is contained 4) addition leukocytes migrate into the region 5)
recruited leukocytes continue to help clear the infection, mainly by phagocytosis. Majorstepsoflocalinflammation
Major Inflammation in detail steps:
• Macrophages detect bacteria using receptor proteins. The resulting attachment
• Also stimulates the macrophages to secrete cytokines, proteins that are secreted
by cells in response to a stimulus.
• Cytokines secreted by macrophages contribute to subsequent steps in
PERMEABILITY OF CAPILLARIES:
• Nearby blood vessels dilate. The capillary walls become more permeable.
• Increased blood flow brings additional leukocytes and defensive proteins into the
• Increased permeability allows these proteins to move into the tissues.
• Leukocytes that gather in these dilated vessels migrate from the blood into the
• Vasodilation and increase capillary permeability are induced by histamine
released from a variety of cells in response to injury.
• Histamine 4 characteristic symptoms: redness, swelling, heat, and pain. As the
capillaries become engorged with blood, the resulting increase in hydrostatic
pressure plus the increased interstitial osmotic pressure that accompanies the
leakage of plasma proteins causes fluid to filter out of the capillaries and into the
tissue spaces, resulting in edema
• The edema exerts pressure against the surrounding tissue and skin, which