Organs Immune System 1

THE ORGANS OF THE THE ORGANS OF THE IMMUNE SYSTEMIMMUNE SYSTEM

Lymphocytes

Lymphocytes

SOURCE OF LYMPHOCYTES

Fetus

PrimaryLymphoid

OrgansSecondaryLymphoid

Organs

Adult

SOURCE OF LYMPHOCYTES

SOURCE OF LYMPHOCYTES

HUMAN THYMUS

PRIMARY LYMPHOID ORGANSTHYMUS (T cell maturation)

(> lymphocytes)

(< lymphocytes)

The functional thymus consists of two cell populations; the stromal cells and the thymocytes. The stromal cells include (1) the subcapsular epithelial cells; (2) the cortical epithelial cells; (3) the medullary epithelial cells; (4) macrophages; and (5) dendritic cells of bone marrow origin. (From Kierszenbaum AL: Histology and cell biology: an introduction to pathology, St Louis, 2002, Mosby.)

MHC-dependiente

Effects of Adult Thymectomy on Immune Response

CHICKEN THYMUS AND BURSA OF FABRICIUS

BURSA OF FABRICIUS(B cell maturation)

follicle

lumen

CortexCortex(lymphocytes, M(lymphocytes, MØ,Ø,

plasma cells)plasma cells)

medullamedulla

Group I (90% Ileum)

Ruminants, Pigs, Horses,Dogs, Humans.

Group II Illeum/Jejunum)

Rabbits, Rodents.

PEYER’S PATCHES

When stimulated by antigen, immunoglobulin A (IgA)-producing B cells are produced in inductive sites, such as the Peyer’s patches.

The role of M cells as antigen-processing cells in the intestinal wall. Antigen that enters enterocytes is usually rapidly degraded in lysosomes. Antigen that enters M cells is not degraded. It may be presented directly to intraepithelial lymphocytes within the M.

Yersinia, M. tuberculosis, Listeria,reovirus, Salmonella.

Structure of the two different types of Peyer’s patch (PP) in sheep. A, An ileal PP at age 8 weeks. B, A PP from the jejunum, also at 8 weeks. Original magnification ×32. (From Reynolds JD, Morris B: Eur J Immunol 13:631, 1983.)

SECONDARY LYMPHOID ORGANSLYMPH NODE

SECONDARY LYMPHOID ORGANSLYMPH NODE

(B cells)

(stimulated)

(T cells)

(unstimulated)

(B cells, macrophages, plasma cells)

SECONDARY LYMPHOID ORGANSLYMPH NODE

secondarysecondaryfolliclefollicle

primaryprimaryfolliclefollicle

medullamedulla

subcapsularsubcapsularsinussinus

dendriticdendriticcellscells

SECONDARY LYMPHOID ORGANSLYMPH NODE

Circulation of Lymphocytes

Lymph Movement.ram

HIGH ENDOTHELIAL VENULES

HIGH ENDOTHELIAL VENULES

HIGH ENDOTHELIAL VENULES

RP

WPB cell follicle

PLS

Marginal Zone

SPLEENSPLEEN

SPLEEN

PERIARTERIOLAR LYMPHOID SHEATS (PALS)

B cells

T cells

arteriole

In Summary

• Specialized tissues (secondary lymphoid organs) concentrate Ag that were introduced through the physical barriers.

• Naïve cells migrate through SLO, where they recognize Ag and initiate an immune response.

• Effector and memory lymphocytes circulate in the blood and to SLO.