Isotype-switched follicular lymphoma displays dissociation between activation-induced cytidine deaminase expression and somatic hypermutation.

In B-cells, activation-induced cytidine deaminase (AID) is required for somatic hypermutation (SHM) and class switch recombination (CSR) of immunoglobulin genes. AID introduces mutations in immunoglobulin variable regions (IGV) during B-cell receptor affinity maturation, but may also introduce aberrant mutations into non-immunoglobulin genes, most commonly BCL6. Follicular lymphoma (FL) B-cells constitutively express AID and undergo CSR, SHM and aberrant SHM. We have studied AID expression, the presence of SHM mutations, CSR, and aberrant SHM in BCL6 in a cohort of 75 FL patients. Whereas IgM-expressing (non-switched) FL were characterized by an expected positive correlation between AID and IGV and BCL6 mutations, isotype-switched FL showed dissociation between AID expression and aberrant SHM, and inverse correlation between SHM and AID expression. Our results unveil two manifest biological subgroups of FL and indicate that the specific dissociation between AID and SHM after isotype switch may correlate with the clinical outcome of this heterogeneous disease.

Histochemical detection of platelet esterase activity in the bone marrow postmortem: can megakaryocytes serve as indicators for time since death?

AIMS: α-Naphthyl acetate esterase (ANAE) is one of the few enzymes that are histochemically detectable on formalin-fixed paraffin-embedded tissue. In bone marrow (BM) biopsies, ANAE staining highlights megakaryocytes. We investigated autopsy BM to determine whether ANAE staining intensity (SI) was associated with postmortem intervals (PMI, period between death and autopsy), and thus could allow the time of death of a patient to be deduced. METHODS: ANAE-stained BM slides of 74 forensic and pathology autopsies as well as 22 biopsies were histologically evaluated and their SIs semiquantitatively graded. RESULTS: ANAE-SIs did not differ between men and women and slightly decreased with age. Biopsies had significantly higher ANAE-SIs than pathology cases. In autopsies, ANAE-SIs were not associated with PMI, except for cases with PMI ≥7 days which were consistently ANAE-negative. CONCLUSIONS: ANAE-SIs in postmortem BM samples were independent of PMI. Thus, ANAE staining of BM megakaryocytes cannot serve as an indicator for time-since-death of a patient.

Post-mortem analysis of bone marrow osteoclasts using tartrate-resistant acid phosphatase staining: does histochemistry work and correlate with time since death?

AIMS: In bone marrow (BM) biopsies, tartrate-resistant acid phosphatase (TRAP) staining represents the gold standard for the characterisation of osteoclasts. TRAP is one of the few enzymes that is histochemically detectable on formalin-fixed paraffin-embedded tissue. This study investigated whether TRAP is also able to visualise BM osteoclasts in autopsy tissue. It was hypothesised that, due to a progressive loss of enzymatic activity in osteoclasts post-mortem, TRAP staining could allow the time of death of a patient to be determined. METHODS: TRAP-stained BM slides of 96 cases including 51 pathology and 23 forensic autopsies and 22 biopsies were histologically evaluated and their staining intensity (SI) semi-quantitatively graded. In the autopsy cases, the results were correlated with the post-mortem interval (PMI, time span in days between death and autopsy). RESULTS: TRAP staining intensities (TRAP-SIs) did not differ between men and women and showed a steady decrease with age. TRAP-SIs were significantly stronger in biopsies than in autopsy cases. Among the autopsies, TRAP-SIs were highly variable and not dependent on PMI, except for three forensic cases with PMI ≥7 days which showed a complete loss of TRAP stainability. On the whole, the TRAP-SIs of pathology and forensic cases did not differ significantly. CONCLUSIONS: This study clearly shows that BM osteoclasts stay TRAP-positive for 7 days post-mortem, although with markedly reduced TRAP-SIs compared with biopsies. Since TRAP-SIs were not correlated with the duration of PMI, TRAP staining of BM osteoclasts cannot serve as a tool to determine the time of death of a patient.

Putative role of TNF-alpha, interleukin-8 and ICAM-1 as indicators of an early inflammatory reaction after burn: a morphological and immunohistochemical study of lung tissue of fire victims.

AIMS: To investigate incipient inflammatory changes as first steps in the development of a systematic inflammatory response syndrome in the lungs of burn victims. METHODS: At the Institute of Legal Medicine of the University Hospital of Freiburg a collection of 40 forensic autopsy cases of burn victims was established that had died within 1 h after fire exposure. This group was compared with a total of 48 autopsy cases in three control groups (postmortem burns vs deaths from haemorrhagic shock vs railway suicide deaths). In all cases, immunohistochemical studies of lung tissue probes were performed to detect the presence of pro-inflammatory mediators using antibodies against tumour necrosis factor α (TNF-α), interleukin-8 (IL-8) and inter-cellular adhesion molecule 1 (ICAM-1). RESULTS: The lungs of burn victims showed a significantly higher extent of intra-alveolar oedema than the other groups. Immunohistochemically, macrophages in all groups mostly showed a distinct expression of TNF-α, but not of IL-8 or ICAM-1. Interestingly, intravascular erythrocytes often showed a positivity of TNF-α that was strongest in the group of burn victims and differed significantly from all the control groups. CONCLUSIONS: In burn victims with short survival times of ≤1 h after fire exposure, the immunohistochemical expression profiles of TNF-α, IL-8 and ICAM-1 in the lungs were not altered enough to prove an instant inflammatory reaction in these cases. Nevertheless, the positive reaction of TNF-α in erythrocytes of burn victims may indicate the beginning of a non-specific immune response to fire-induced inhalation trauma.