02c Lymphoid Immune Tissues

Generative lymphoid organs of adult mammals are

• Bone marrow (B)

• Thymus (T)

B cells partially mature in the ..?

Bone Marrow;

1. enter circulation

2. populate peripheral lymphoid organs (spleen and lymph nodes)

3. Complete maturation

T cell mature in the …?

In thymus

1. Enter circulation

2. Populate peripheral lymphoid organs and tissues

Generative organs …?

provide growth factors for lymphocytes maturation and provide antigens for self recognition and selection of maturing lymphocytes

The Peripheral lymphoid organs are …?

1. Spleen

2. Lymph nodes

3. cutaneous immunes system

4. mucosal immunes system

Peripheral lymphoid organs share ???

Common function

• delivery of antigen

• Responding naive lymphocytes to an inflammatory site

• Anatomic segregation of B and T

Bone Marrow

• GENERATION SITE OF ALL BLOOD CELLS

  • COME FROM HEMATOPETIOC STEM CELLS (HSC)

• proliferation and maturation of blood cell is stimulated by cytokines

HEMATOPETIOC STEM CELLS (HSC)

• self-renewing

• identifiable by surface markers

HEMATOPETIOC STEM CELLS (HSC) give rise to

two types of multipotent cells:

1. Common lymphoid progenitor

2. Common myeloid progenitor

Thymus

• bilobed organ

• lobes consist of the outer cortex and inner medulla

• only mature T cells leave the thymus

Cortex

Dense collection of T Cells

Maturing of T Cells ??

beings in the cortex then migrate toward the medulla

• the medulla contains mostly mature T Cells

Lymphatic System

• specialized vessel that drain fluid from tissues

  • drain into and out of lymph nodes —> then blood

Lymphatic capillaries absorb fluid from …?

tissues and around cells

• all free uptake of interstitial fluid and act as on-way values to prevent blackflow

What is lymph

fluid from tissues and around cell that enter the lymphatic capillaries

Lymph is pumped in …

Afferent to Efferent

Progressively larger vessel by the contraction of PERILYMPHATIC SMOOTH MUSCLE and pressure

• mergers into afferent lymphatics that drain lymph noes

• goes into efferent lymphatics

at the end of a lymph nodes chain …?

lymph empties into lymph vessels that empty into the thoracic duct

• duct empites into superior vena cava

• then back into the stream

how much lymph is normally return to circulation per day??

~ 2L

What else can enter lymphatic vessels

• Dendritic cells capture microbial agents and enter

• microbial agents also enter on their own

• Chemokine from inflammatory sites also enter lymphatics

What do lymph nodes filter?

antigen and DC-antigens to present to the adaptive immune system before they enter the blood stream

Lymph nodes

encapsulated, vascularized secondary lymphoid organs

• anatomic feature promote initiation of adaptive immunes response to antigen in the lymphatic system

Lymph nodes are surrounded by

• Fibrous capsule

Inside the lymph node the sinus is lined by?

-Reticular cells cross-bridged by fibrils of collagen and other extracellular matrix protein and filled with:

• Lymph

• Macrophages

• Dendritic cells

Afferent lymphatic empty into …?

subcapsular (marignal) sinus

• lymphocytes-rich cortex beneath the subscapular sinus

• The outer cortex contains follicles

  • Secondary have germinal centers

  • Primary don’t

  • Germinal center = activation of B cells

B cells and T cells are in different regions of the cortex of the lymph nodes. What’s the difference?

Each section has a unique architecture of reticular fibers and stromal cells ‘

• follicles are B cell zones

Why do germinal center develop?

In response to Antigen stimulation

B cell proliferation???

• selection of B cells producing high-affinity antibodies

• generation of memory B cells

• generation of long-lived plasma cells

T cell in the Lymph nodes? Where? What they do?

• located beneath and more central than follicles

• naive T Cells enter the lymph nodes from blood and into the T cell zone

• Naive B and T enter through the artery and enter the stroma of the node

Cytokines called chemokines determine ….?

where B and T cells reside in the nodes

• Through binding of receptor

• chemokines are a large family of 8 - 10 kDA cytokines

B and T cell segregation ensures

they will react w/ proper APC

Antigen activation of B and T cell causes:

• T Cells migrate towards follicles to help B cells exit node and enter circulation

• B Cells migrate to germinal center and differentiate into plasma cell and may travel back to the bone marrow

Viruses and high Molecular weight (MW) antigens are taken up by …?

sinus macrophages and presented to B cells

Low molecular eight (MW) soluble antigens are taken up by … ?

• resident DC and can be presented to T cells

  • need tissue DC to present antigen to T cells for larger sustaibed response

Splenic parenchyma is …?

Anatomically and functional divided into:

• red-pulp

  • blood filled vascular sinusoids

• white pulp

  • lymphocytes-rich

  • promotes adaptive immune responses to blood-borne antigens

Red pulp macrophages …?

important filter for the blood

• remove microbes

• damaged cells

• antibody-coated cells and microbes