The peptide FA-LL-37, previously termed FALL-39, was originally predicted from an ORF of a cDNA clone isolated from a human bone marrow library. This peptide was synthesized and found to have antibacterial activity. We have now characterized and sequenced the complete gene for FA-LL-37, termed FALL39. It is a compact gene of 1963 bp with four exons. Exons 1-3 code for a signal sequence and the cathelin region. Exon 4 contains the information for the mature antibacterial peptide. Our results indicate that FALL39 is the only member of the cathelin gene family present in the human genome. Potential binding sites for acute-phase-response factors are identified in the promoter and in intron 2. A possible role for the cytokine interleukin-6 in the regulation of FA LL39 is discussed. Anti-(FA-LL-37) IgG located the peptide in granulocytes and we isolated the mature peptide from these cells after degranulation. Structural analysis determined the mature peptide to be LL-37. To obtain LL-37 for antibacterial assays, synthetic FA-LL-37 was degraded with dipeptidyl-peptidase I. This analysis showed that mature LL-37 is a potent antibacterial peptide.

A 78 residue antimicrobial, basic peptide, NK‐lysin, with three intrachain disulfide bonds was purified from pig small intestine and characterized. A corresponding clone was isolated from a porcine bone marrow cDNA library. The 780 bp DNA sequence had a reading frame of 129 amino acids which corresponded to NK‐lysin. The clone was used to show that stimulation with human interleukin‐2 induced synthesis of NK‐lysin‐specific mRNA in a lymphocyte fraction enriched for T and NK cells. Lower levels of mRNA were detected in tissues known to contain T and NK cells, such as small intestine, spleen and colon. Interleukin‐2 also induced both proliferation of the lymphocyte fraction and cytolytic function in these cells. Immunostaining showed that NK‐lysin was present in cells positive for CD8, CD2 and CD4. NK‐lysin showed high anti‐bacterial activity against Escherichia coli and Bacillus megaterium and moderate activity against Acinetobacter calcoaceticus and Streptococcus pyogenes. The peptide showed a marked lytic activity against an NK‐sensitive mouse tumour cell line, YAC‐1, but it did not lyse red blood cells. The amino acid sequence of NK‐lysin exhibits 33% identity with a putative human preproprotein, NKG5, of unknown function but derived from a cDNA clone of activated NK cells. We suggest that NK‐lysin is a new effector molecule of cytotoxic T and NK cells.

We identified antibacterial components in human T and natural killer (NK) cells by using freshly isolated lymphocytes enriched for T and NK cells as starting material. After growing these lymphocytes for 5 days in the presence of interleukin (IL)–2, we isolated and characterized several antibacterial peptides/proteins from the supernatant—α-defensins (HNP 1-3), LL-37, lysozyme, and a fragment of histone H2B—although other active components were also present. We then used reverse transcriptase–polymerase chain reaction to search for expression of the gene coding for LL-37 in several B-cell lines, γδ T-cell lines, NK clones, and one monocytic cell line, with positive results, but found no expression in several αβ T-cell lines. The α-defensins (HNP 1-3) were also found to be expressed in several of these cell lines. To confirm the presence of these antibacterial peptides in lymphocytes, we localized them to NK, γδ T cells, B cells, and monocytes/macrophages by using double-staining immunohistochemical analysis of freshly isolated lymphocytes. We also found that primary cultures of lymphocytes transcribe and secrete LL-37 and that these processes are affected by IL-6 and interferon-γ. In addition, we demonstrated that LL-37 has chemotactic activity for polymorphonuclear leukocytes and CD4 T lymphocytes, whereas others have shown chemotactic activity for human α-defensins (HNP 1-2). These findings suggest that microbicidal peptides are effector molecules of lymphocytes and that antibacterial activity previously shown to be derived from T and NK cells may be partly mediated by the antibacterial peptides LL-37 and HNP 1-3.

Aim. The aim of this retrospective study is to illustrate clinical utility and impact of pulmonary embolism (PE) diagnostics of up to date Ventilation ⁄ Perfusion SPECT (V ⁄ P SPECT ) applying holistic interpretation criteria.Material and methods. During a 2-year period 2328 consecutive patients referred to V ⁄ P SPECT for clinically suspected PE were examined. Final diagnosis was established by physicians clinically responsible for patient care. To establish the performance of V ⁄ P SPECT negative for PE, patients were followed up by medical records for 6 months.Results. Ventilation ⁄ Perfusion SPECT was feasible in 99% of the patients. Data for follow-up were available in 1785 patients (77%). PE was reported in 607 patients (34%). Normal pattern was described in 420 patients (25%). Pathology other than PE such as a pneumonia, left heart failure, obstructive lung disease, tumour was described in 724 patients (41%). Report was nondiagnostic in 19 patients (1%). Six cases were classified as falsely negative because PE was diagnosed at follow-up and was fatal in one case. Six cases were classified as falsely positive because the clinician decided not to treat. In 608 patients with final PE diagnosis, 601 patients had positive V ⁄ P SPECT (99%). In 1177 patients without final PE diagnosis 1153 patients had negative V ⁄ P SPECT (98%).Conclusions. Holistic interpretation of V ⁄ P SPECT, yields high negative and positive predictive values and only 1% of nondiagnostic findings and was feasible in 99% of patients. It is a responsibility and a challenge of nuclear medicine to provide optimal care of patients with suspected PE by making V ⁄ P SPECT available.

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