Rejection is a complex process in which
“recepient immune system recognize
the graft as foreign and attacks it”.
1. Cell mediated immunity
2. Circulating antibodies
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.
1. Direct pathway
2. Indirect pathway
It is called humoral rejections.
Presence of preformed antidonor
Transplant rejection has already occurred.
Initial exposure to class I&II HLA
Antibodies causes injury by
1. Complement dependent
3. Antibody dependent cell
Occurs within minutes or hours after
Immunoglobulin and complement
Neutrophils accumulate leading to
occlusion of capillaries & fibrinoid necrosis.
Cellular – mononuclear cell infiltrate
Humoral – vasculitis
Seen within initial months after
Mononuclear cells accumulates in
glomerular and peritubular capillaries
leading to FOCAL TUBULAR NECROSIS.
Treatment – cyclosporin.
Also known as rejection vasculitis.
Necrotizing vasculitis characterised by
Presence of complement breakdown
product C4d – indicator of humoral
Treatment – B cell depleting agents.
Prevention of host T cells from
receiving co-stimulatory signals (B7-
1&2) from dendritic cells.
EBV induced lymphoma
HPV induced squamous cell carcinoma
Hematopoietic stem cell transplants are
1. Hematological malignancy
2. Aplastic anemia
4. Non hematological cancers
2. GVH disease
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
It may be
Days to weeks after allogenic bonemarrow
1. Generalised rash
3. Ulceration of gut
4. Bloody diarrhea
Follow acute syndrome or occur insidiously.
1. Cutaneous injury
2. Cholestatic jaundice
3. Esophageal strictures
4. Depletion of lymphocytes
It is a life threatning condition.
Treatment – bonemarrow transplants.