Page 128 - Concise Pathology for Exam Preparation ( PDFDrive )

5 Diseases of Immunity 113

Problems With Bone Marrow Transplantation (BMT)

• �GVHD (graft-versus-host disease)
• �Transplant rejection
• �Immunodeficiency
GVHD occurs in any situation in which immunologically competent cells or their precur-
sors are transplanted into immunologically crippled recipients and the transferred cells
recognize alloantigens in the host, eg, BMT, transfusion of solid organs rich in lymphoid
cells, and transfusion of nonirradiated blood (Flowchart 5.11).

Above recipients receive bone marrow cells from allogenic donors

Immunocompetent T cells present in the donor marrow recognize the recipient’s HLA antigens as foreign and
react to them

Both CD4+ and CD8+ T cells recognize and attack host tissues
FLOWCHART 5.11. Mechanism of GVHD.

GVHD may be
Acute
(a)
(i) Occurs days to weeks after transplant

(ii) Causes considerable damage mediated by cytokines without infiltration of lymphocytes

(iii) Any organ may be affected

(iv) Major clinical manifestations result from involvement of immune system, epithelia

of the skin, liver and intestines, eg, generalized rash with desquamation, mucosal

ulceration with bloody diarrhoea and jaundice
(b)
Chronic
(i) May follow acute GVHD or occur insidiously

(ii) Characterized by extensive cutaneous injury, destruction of skin appendages and

fibrosis of dermis (differential systemic sclerosis)

(iii) Manifests with chronic liver damage with cholestasis, oesophageal strictures and
life-threatening infections (due to involution of thymus and depletion of lympho-
cytes in lymph nodes)
Q. Describe the physical and chemical nature of amyloid.
Ans. Amyloid is an amorphous, eosinophilic, pathologic, proteinaceous substance depos-
ited in between cells or extracellularly.
• �First described by Rokitansky in 1842; it was named ‘amyloid’ by Virchow. It is not a
distinct entity but a group of diseases having in common deposition of similar appearing
proteins constituted by insoluble abnormal fibrils that injure tissue.
• �The fibrils are formed by the aggregation of misfolded, abnormally soluble proteins
which bind to various proteoglycans and glycosaminoglycans (heparin and dermatan
sulphate and serum amyloid P protein or SAP). Amyloid was so named because the
charged sugar groups in the adsorbed proteins resulted in a staining pattern similar to
amylase, it was however later found to be unrelated to starch.
Physical Nature of Amyloid
The main physical constituents of amyloid are nonbranching fibrils of indefinite length
and a diameter of 7.5–10 nm, which on X-ray crystallography and infrared spectroscopy

show a cross-b-pleated sheet conformation

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