allograft rejection immunology

1. Mechanisms of Allograft
Rejection
By
M.sri aravind lal
B841018
M.sc genomics

2. Introduction
• Transplantation refer to the act of transferring
cells, tissues or organs from one site to another .
• Disease can becured by implanation of a healthy
organ, tisssues or cells (a graft) from one
individual to another.
• The first successful human transplant which was
between identical twins accomplished in boston
in 1954.

3. Immunological basis of allograft
rejection
• Allograft is tissue transferred between
genetically different memberof the same
species.In mice,an allograft is performed by
transferring tissue or an organ from one strain
to another.
• In humans,organ grafts from one individual to
another are allografts unless the donor and
recipient are identical twins.

4. Allograft rejection display specificity
and memory
• The rate of allograft rejection varies according to
the tissues involved.skin graft is faster than
other tissue such as kidney or heart.
• If an inberd mouse of strain A is grafted with
skin from strain B,primary graft rejection,known
as first set rejection occurs.
• The vascularized transplant becomes infiltrated
with lymphocytes,monocytes,neutrophils, other
inflammatory cells.

6. CONT………
• There is decreased vascularization of the
transplanted tissue by 7-10 days, visible necrosis
by 10 days and complete rejection by 12-14 days.
• Immunologic memory is demonstrated when a
second strain Bgraft is transferred tona grafted
strain A mouse.
• Complete rejection occur within 5-6 days –
second set rejection

7. Graft rejection occurs in two stages
• Graft rejection is caused by a cell mediated
immuno response to alloantigen expressed on
cells of graft
• SENSITIZATION STAGE
• CD4+ and CD8+ T cells recognize alloantigen
exprssed on cells of foreign graft and induces
Tcell proliferation in the host.
• EFFECTOR STAGE
• Immune destruction of graft take place.

8. CONT….

9. Graft rejection reaction
• HYPERACUTE REJECTION REACTIONS
• Occurs within 24 hours of transpolantation
• Preexisting host serum antibody specific for
antigen of graft.
• ACUTE REJECTION REACTIONS
• Mediated by Tcell responses and begin about in
10 days after tranplantation.
• CHRONIC REJECTION REACTION
• occurs from months to years after
transplantation by both humoral and cell
mediated responses by the recipient

10. Steps in hyperacute rejection