Feline lung-digit syndrome: unusual metastatic patterns of primary lung tumours in cats.

PRACTICAL RELEVANCE: Feline 'lung-digit syndrome' describes an unusual pattern of metastasis that is seen with various types of primary lung tumours, particularly bronchial and bronchioalveolar adenocarcinoma. Tumour metastases are found at atypical sites, notably the distal phalanges of the limbs; the weightbearing digits are most frequently affected, and multiple-digit and multiple-limb involvement is common. Often primary lung tumours in cats are not detected because of clinical signs referable to the primary tumour; rather, many cases present with signs referable to distant metastases. Other sites of metastases from feline primary lung tumours include the skin, eyes, skeletal muscle and bone, as well as multiple thoracic and abdominal organs. These lesions are thought to arise from direct arterial embolisation from the tumour. Indeed tumour embolisation to the aortic trifurcation is possible. PATIENT GROUP: Primary lung neoplasms are uncommon in the cat. Older animals are most affected (mean age at presentation 12 years, range 2-20 years). There is no apparent sex or breed predilection. CLINICAL CHALLENGES: Feline lung-digit syndrome presents a diagnostic challenge. Typically there is swelling and reddening of the digit, purulent discharge from the nail bed, and dysplasia or fixed exsheathment of the associated nail. While these signs might be suggestive of infection, this could be secondary to a digital metastatic lesion, particularly in a middle-aged or elderly cat. Radiographic evidence of extensive bony lysis of the distal phalanx, which can be trans-articular to the second phalanx, raises the index of clinical suspicion for metastasis of a primary pulmonary tumour. Thoracic radiography is warranted prior to any surgery or digital amputation as the prognosis is generally grave for cats with this syndrome, with a mean survival time of only 58 days after presentation. EVIDENCE BASE: This article reviews the previous literature and case reports of feline lung-digit syndrome and feline primary pulmonary neoplasia in general, discussing the course of this disease and the varying clinical presentations associated with different sites of metastasis.

Conservation of mucosal associated invariant T (MAIT) cells and the MR1 restriction element in ruminants, and abundance of MAIT cells in spleen.

MHC-related protein 1 (MR1) is a highly conserved MHC class I-like molecule. Human and murine mucosal associated invariant T (MAIT) cells are restricted by MR1 and express an invariant T cell receptor. Even though MR1 protein expression on the cell surface has not been demonstrated in vivo or ex vivo, it is assumed that MR1 presents a bacterial antigen from the intestinal lumen to MAIT cells because MAIT cells are present in the lamina propria and their expansion is dependent on the presence of intestinal micro flora. The existence of bovine MAIT cells and MR1 has been demonstrated recently although ovine MAIT cells and MR1 have not yet been described. We cloned bovine and ovine MR1 transcripts, including splice variants, and identified an anti human MR1 antibody that recognizes cells transfected with the bovine homolog. Using this antibody, no MR1 staining was detected using cells freshly isolated from blood, thymus, spleen, colon, ileum, and lymph node. MAIT cells are known to be enriched in the CD4/CD8 double negative peripheral blood T cell population, but their relative abundance in different tissues is not known. Comparison of the amount of MAIT cell-specific TCR transcript to the amount of constant alpha chain transcript revealed that numbers of MAIT cells are low in neonates and increase by 3-weeks of age. In 3-month old animals, MAIT cells are abundant in spleen and less so in ileum, peripheral blood, lymph node, colon, and thymus.