Sandbox: T cell
Overview
Pathogenesis
- Adult T‐cell leukaemia/lymphoma (ATLL) is a mature T‐cell neoplasm of post‐thymic lymphocytes
- Etiologically linked to the human T‐cell lymphotropic virus, HTLV‐I, HTLV‐I serology is a mandatory investigation
- Long latency, virus exposure usually occurs very early in life
- Transmission of HTLV-1 is believed to occur from mother to child; by sexual contact; and through exposure to contaminated blood, either through blood transfusion or sharing of contaminated needles
- HTLV-I p40 tax viral protein: non structural protein that causes transcriptional activation of many genes in infected lymphocytes
- Enhancement of c-AMP response element binding transcription factor (CREB) phosphorylation
- HTLV-I basic leucine zipper factor (HBZ): causes T cell proliferation and oncogenesis
- JAK/STAT pathway constitutively activated in HTLV-I infected cells
- The disease manifests in 75% of cases with leukaemia and in the remaining as a pure lymphomatous form
- widely disseminated disease which may involve liver, skin dermis layer, peripheral blood involvement , bone, and CNS
- anaemia and thrombocytopenia is variable
- patchy infiltrates Bone marrow infiltration
- Neutrophilia and eosinophilia Present
- lytic bone lesions
- tumor-induced osteolysis hypercalcaemia
- increased osteoclastic activity
- elevated serum levels of IL-1, TGFβ, PTHrP, macrophage inflammatory protein (MIP-1α), and receptor activator of nuclear factor-κB ligand (RANKL) have been associated with hypercalcemia
- Diffuse infiltration of the lymph node leading expansion of the paracortical area
- Infiltration of the dermis skin infiltration, epidermotropism present and Pautrier's microabcesses
- antibodies to HTLV‐I are demonstrable
- defects of cell-mediated immunity recurrent infections
Genetic
- +3, +7, +21, monosomy X,deletion of chromosome Y and chromosomes 6 and 14q;
- 14q11 and break points e TCR‐alpha and ‐delta chain genes TCRA and TCRD
- 14q32 of TCL1
- mutations of tumour‐suppressor genes CDKN2A (p16), CDKN2B (p15) and TP53 (p53)
Gross
- Nodules skin
Micro
- pleomorphic, a medium size lymphocyte conndensed chromatin
- convoluted or polylobated nucleus
- nucleoli are not visibl
- cytoplasm agranular
- “flower cell”
- Reed-Sternberg like cells may also be present
- CD4 positive CD8 positive
- CD2 and CD5 positive
- CD7 negativ
- CD3 and T‐cell receptor (TCR)‐β may be down‐regulated
- CD2, CD3, CD4, CD5, CD25, TCR α/β, CD45ROCD56 expressionCCR4, FOXP3, HLA-DR, L-selectin (CD62), MUM-1