2. Lymphocytes
•
Lymphocytes constitute about 20% of the total blood
leukocytesThe. two major populations of lymphocytes
•
B-cell :are lymphocytes that develop in the fetal liver
and subsequently in bone marrow.
•
T-cell:are lymphocytes that develop in the thymus.
This organ is seeded by lymphocytic stem cells from
the bone marrow during embryonic development.
3. Origin of B-cell
•
Some lymphoid cells develop and mature
within the bone marrow and are referred
to as B cells (B for bursa of Fabricius, or
bone marrow). The function of bursa of
Fabricius in birds is played by bone
marrow in humans.
4. Origin of T-cell
Thymus is the site where a large diversity of T
cells is produced and so they can recognize
and act against a myriad number of antigen–
MHCs (major histocompatibility complexes)
5.
6.
7. Types of B-cell
B1
1-The B1 subset was originally distinguished by the
phenotype CD5+, CD43+, CD23
2- B1 cells develop early
3-have a more limited range of receptors
8. B2
In adults most B cells are of the B2 subset
-
1
2-generate a wide range of antigen receptors
9. Types of T-cell
1- γδ T cells:consist <5% of the total T cells
2-Intraepithelial lymphocyte s (IELs) are mixed populations of
cells found in submucosal tissues.
3-Cytotoxic T lymphocytes (CTLs/Tc) are capable of destroying
virally infected or allogeneic cells
4-Helper T (Th) cells perform a number of functions, including
helping B cells to divide,
5-Regulatory T cells (Treg), identified by the expression of the
transcription factor Foxp3 erentiate, and secrete antibody,
10. Types of Th
-Th1 cells can recognize antigen presented by
mononuclear phagocytes
-Th1 can modulate the antibody response by
affecting the classes of immunoglobulin
produced.
11. •
-Th2 cells by IL-4
-Th2 cells can modulate the antibody
response
Th2 cells release cytokines
-
12. -Th17 cells by transforming growth factor-β
-Th17 cells release cytokines that promote
inflammatory responses,
