Rejection is a complex process where the recipient's immune system attacks the transplanted organ or graft as foreign. It involves both cell-mediated and antibody-mediated immunity. There are three main types of rejection: hyperacute rejection which occurs within minutes/hours due to pre-existing antibodies, acute rejection within months due to an immune response, and chronic rejection over longer periods due to inflammation. Preventing rejection requires immunosuppressive drugs or techniques to block co-stimulatory signals needed for an immune response.

1. BALAJI.R
ALTHEANZ 09’

2.  Rejection is a complex process in which
“recepient immune system recognize
the graft as foreign and attacks it”.
 It involves
1. Cell mediated immunity
2. Circulating antibodies

3.  It is caused by T-cell mediated reactions.
 Destruction of grafts occurs by
1. CD8+ CTLs
2. CD4+ helper cells
 Delayed hypersensitivity is triggered by
CD4+ helper cells.
 2 pathways
1. Direct pathway
2. Indirect pathway

5.  It is called humoral rejections.
 2 types
1. Hyperacute
2. Acute
HYPERACUTE:
 Presence of preformed antidonor
antibodies.
 Transplant rejection has already occurred.

6. ACUTE:
 Initial exposure to class I&II HLA
antigens.
 Antibodies causes injury by
1. Complement dependent
cytotoxicity
2. Inflammation
3. Antibody dependent cell
mediated cytotoxicity.

7.  Rejection reactions
1. Hyperacute
2. Acute
a. cellular
b. humoral
3. Chronic

8.  Occurs within minutes or hours after
transplantation.
 Kidney becomes
1. Cyanotic
2. Mottled
3. Flaccid
 Immunoglobulin and complement
deposition occurs.
 Neutrophils accumulate leading to
occlusion of capillaries & fibrinoid necrosis.

10.  Cellular – mononuclear cell infiltrate
 Humoral – vasculitis
ACUTE CELLULAR:
 Seen within initial months after
transplantation.
 Mononuclear cells accumulates in
glomerular and peritubular capillaries
leading to FOCAL TUBULAR NECROSIS.
 Treatment – cyclosporin.

12.  Also known as rejection vasculitis.
 Necrotizing vasculitis characterised by
intimal thickening.
 Presence of complement breakdown
product C4d – indicator of humoral
rejection.
 Treatment – B cell depleting agents.

16.  Immunosuppressive agents
1. Cyclosporin
2. Azathioprine
3. Steroids
4. Rapamycin
5. Monoclonal antibodies.

17. ANOTHER METHOD:
 Prevention of host T cells from
receiving co-stimulatory signals (B7-
1&2) from dendritic cells.
DISADVANTAGES:
 EBV induced lymphoma
 HPV induced squamous cell carcinoma
 Kaposi sarcoma

18.  Hematopoietic stem cell transplants are
used for
1. Hematological malignancy
2. Aplastic anemia
3. Thalassemia
4. Non hematological cancers
PROBLEMS:
1. Immunodeficiency
2. GVH disease

19.  Occurs in any situation in which
“immunologically competent cells or their
precursors are transplanted to
immunologically crippled recipients and the
transferred cells recognize allo-antigens in
the host”.
 It may be
1. Acute
2. Chronic

20.  Days to weeks after allogenic bonemarrow
transplantation.
 Clinical features
1. Generalised rash
2. Jaundice
3. Ulceration of gut
4. Bloody diarrhea

21.  Follow acute syndrome or occur insidiously.
 Clinical features
1. Cutaneous injury
2. Cholestatic jaundice
3. Esophageal strictures
4. Depletion of lymphocytes
 It is a life threatning condition.
 Treatment – bonemarrow transplants.