Lymphocytes and Lymphoid

Tissues

Basic Pathway

Figure 2-3

Lymphocytes and Lymphoid Tissues

• Primary lymphoid tissues

(thymus and bone marrow), • Secondary lymphoid tissues

(lymph nodes, Peyer’s patches, and spleen)

• Tertiary lymphoid tissues(skin and mucosal lamina propria)

Components of the Immune System

I. Bone Marrow - Hematopoietic Stem Cells

• Myeloid progenitor– neutrophils -macrophage– basophils - mast cells– eosinophils

• Common lymphoid progenitor– T-lymphocytes– B-lymphocytes

Hematopoiesis

Hematopoiesis is driven by cytokines:

stem cell factor; IL-3; GM-CSF; G-CSF; M-CSF; IL-7 IL-11

Hematopoiesis

•Erythrocyte-stimulated by EPO (Amgen) EPO = erythropoietin

•Megakaryocyte/Platelets-stimulated by IL-11

•Granulocyte/Monocyte-stimulated by GM-CSF, G-CSF, and M-CSF

•Lymphocyte -stimulated by IL-7

IL-7

Cyto

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wth

facto

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Lymphoid System

MALT = mucosal associated lymphoid tissue

Lymphocyte Maturation

Stem Cell

Naïve or virgin lymphocytes migrate to secondary lymphoid organs

(short lived)

ActivationMemory-Effector cells

Key Concept

Thymus

T-Lymphocyte Maturation

Thymus

The thymusthymus is an organ strictly dedicated to the selection and differentiation of T lymphocytes.

The T cell precursor cells originate in the bone marrow and then go through a series of developmental steps resulting in the production of a population of mature, antigen-sensitive T-cells.

Thymus The thymus is made up of a cortex and a

medulla. The cortex consists of densely packed

immature thymocytes, macrophages, and dendritic cells supported by a thymus stroma largely made up of epithelial cells.

The medulla contains mainly mature thymocytes and macrophages (and a stroma), and the cells are much less dense.

Thymus

Cortex

Medulla

NeonatalThymus

YoungerThymusCortex

YoungerThymusMedulla

Hassall’s corpusclesare tightly packedepithelial cells fromdegenerating cells.

AdultThymusatrophiesat puberty

Clonal Selection-Thymus

• Each lymphocyte bears a single antigen Each lymphocyte bears a single antigen specificityspecificity

• The a high affinity interaction between The a high affinity interaction between the antigen and the T-cell leads to the antigen and the T-cell leads to lymphocyte activation.lymphocyte activation.

• Effector cells derived from the activated Effector cells derived from the activated lymphocyte will bear identical receptors lymphocyte will bear identical receptors as the parent cell.as the parent cell.

• Lymphocyte bearing binding receptors Lymphocyte bearing binding receptors for self-antigens are normally deletedfor self-antigens are normally deleted.

Thymicprocessingof T-cells

Thymicprocessingof T-cells

See notes

T-Lymphocytes• T-cells

– Cellular mediated immunity– Antigen-presentation– Major histocompatibility

Complex (MHC)

– T-cell Subsets– CD4 (Th1 and Th2)– CD8

B-lymphocytes

B-Lymphocytes

B-Cells - Humoral Immunity

•B-cell lineage synthesize immunoglobulins

virgin

Memory

Plasma

B-Cells - Humoral Immunity

• Secretion of certain lymphokines– IL-6 IgM– IL-6, 4,11 IgG– IL-6, 2,5, TGF- IgA– IL-6, 4 IgE

• Present Antigen to T-cells

T-Lymphocytes

T-cytotoxic

B-cell

T-helperAPC

LymphocyteCirculation

Thoracic Duct

Figure 2-1

Figure 2-1

Lymph Node

Lymph Node

Lymph Node

Spleen

CompletePathway

KNOW

Question

1._____After birth, human B-lymphocyte differentiation takes place in the

A. Bone marrowB. LiverC. Gut-associated lymphoid tissueD. Spleen germinal centerE. Peyer's patches

Question

2._____ The characteristic of the innate immune response is:

A. Has memoryB. Occurs in minutes to hoursC. Takes about 5 days to be effectiveD. Requires antigen presentation by antigen

presenting cellsE. Involves the formation of immunoglobulins

Question3._____ The acute-phase (formation of

acute phase proteins) response:A. Is stimulated by interleukin-1,

interleukin-6, tumor necrosis factor-, interferon-

B. Is a recent marker of coronary heart disease

C. Facilitates the phagocytosis of bacteriaD. Is an immunological marker of chronic

inflammatory diseaseE. All of the above

Question

4._____Chemotaxis means:

A. Phagocytosis of bacteriaB. Clonal elimination of B-cellsC. Induction of migration of an

immune cellD. Adhesion of immune cells to the

vascular endothelial cellsE. Isotype switch from IgM to IgE

Question5._____ Interferons were first

characterized by their:

A. Enhancement of B cell proliferationB. Antiviral activitiesC. Cytotoxicity of transformed cellsD. Activation factor for eosinophilsE. Stimulation of growth of precursors

of all the hemopoietic lineage

Question6.____A plasma cell secretes:

A. Antibody of identical specificity to that on the surface of the parent B-cell.

B. Antibody of two antigen specificities.C. The antigen it recognizes.D. Antibodies that recognize numerous

antigensE. Lysozyme.

Question7._____ Secondary lymphoid tissues

include:

A. Bone marrow and thymusB. Skin, mucosal surfacesC. Neutrophils and eosinophilsD. ComplementE. Thymus, lymph nodes, spleen,

MALT, and BALT tissues

Question8.____CD8 is a marker of:

A. B-cellsB. Helper T-cellsC. Cytotoxic T-cellsD. An activated macrophageE. A polymorph precursor

Question9._____Specific antibodies are readily

detectable in serum following primary contact with antigen after:

A. After 10 minutes.B. Within 1 hour.C. By 5—7 days.D. After 3—5 weeks.E. Only detectable after a second contact

with antigen.

Question10._____Which of the following is a

well-known effect of interleukin-8?

A. Attraction and activation of neutrophils

B. Induction of B-cell proliferationC. Induction of the switch from IgM to

IgG synthesisD. Induction of B-cell differentiationE. Suppression of interleukin release

by helper T cells

Monday’s class

• There will be no class due to the MLK holiday.