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Lipid antigens are presented to T cells by the CD1 family of proteins. In this study, we characterize the complete dog (Canis familiaris) CD1 locus, which is located on chromosome 38. The canine locus contains eight CD1A genes (canCD1A), of which five are pseudogenes, one canCD1B, one canCD1C, one canCD1D, and one canCD1E gene. In vivo expression of canine CD1 proteins was shown for canCD1a6, canCD1a8, and canCD1b, using a panel of anti-CD1 monoclonal antibodies (mAbs). CanCD1a6 and canCD1a8 are recognized by two distinct mAbs. Furthermore, we show differential transcription of the three canCD1A genes in canine tissues. In canine skin, the transcription level of canCD1A8 was higher than that of canCD1A6, and no transcription of canCD1A2 was detected. Based on protein modeling and protein sequence alignment, we predict that both canine CD1a proteins can bind different glycolipids in their groove. Besides differences in ectodomain structure, we observed the unique presence of three types of cytoplasmic tails encoded by canCD1A genes. cDNA sequencing and expressed sequence tag sequences confirmed the existence of a short, human CD1a-like cytoplasmic tail of four amino acids, of an intermediate length form of 15 amino acids, and of a long form of 31 amino acids.

For the development of vaccines and treatments against tuberculosis, animal models are needed. In this review, the pathogenesis and immune responses during human and bovine tuberculosis will be compared. Special attention will be paid to latency, because this feature has recently become the basis of specialized vaccines against latency antigens.

Tissue-specific distribution of gammadelta TCRs with limited TCR diversity is a common phenomenon in species with a low percentage of gammadelta T cells like humans and mice. We set out to investigate whether this is also the case in cattle (Bos taurus), a species with high percentages of gammadelta T cells. Using a method that was independent of variable (V) segment-specific primers, we generated 65 unique TCR delta chain sequences. We found no evidence for preferential use of certain Vdelta segments in lymph node, skin, spleen, small intestine, large intestine, and blood. The delta chain CDR3 length distribution was very wide in each tissue, which was confirmed by spectratyping. The highly variable CDR3 length was due to the use of up to four diversity (D) segments by one bovine delta chain. Human and murine delta chains contain only one or two D segments. The five functional Ddelta segments that we describe here were identified at cDNA and genomic level, and are the first ruminant D segments described. Fourteen TCR delta chain sequences used novel Vdelta1 segments, and one expressed a novel member of the Vdelta3 family. The number of known functional Vdelta segments in cattle including these new ones is 42 now, but the total number may be much higher. A high number of Vdelta segments in combination with the use of up to four out of five D segments, and the possibility of using non-template encoded (N) nucleotides on either side of these, makes the potential bovine delta chain repertoire much bigger than any known TCR chain. This situation is quite different from the situation in humans and mice, and suggests that the differences between gammadelta high and gammadelta low species in distribution, diversity, and function of gammadelta T cells may be substantial.

In all species studied so far, gammadelta T cells are abundantly present in epithelia. The functions of these cells are largely unknown. Using a lymph duct cannulation method, which is only possible in large animals such as cattle, we show that large numbers of gammadelta T cells, but not alphabeta T cells, are constitutively present in pseudoafferent lymph draining bovine skin. The gammadelta T cells, which are present in pseudoafferent lymph, use Vgamma segments that are characteristic for bovine dermal gammadelta T cells, suggesting that these cells migrated from the skin. Further supporting the origin of these cells is the fact that fluorescent latex beads injected in the skin could be recovered in cells in the pseudoafferent lymph. The cannulation method is minimally invasive, and the lymph flow, which was sustained and remained essentially unaltered during 14 days, closely represents the in vivo situation. The gammadelta T cells could not be induced to produce IFN-gamma, TNF-alpha, and IL-10, and they did not express costimulatory molecules, IL-2 receptor, and MHC Class II molecules. The level of gammadelta T cell egress was 6.7x10(3) gammadelta T cells per cm2 skin per hour, which is enough to deplete all gammadelta T cells from the skin within 46 h. As this massive gammadelta T cell migration was observed during 14 days, constant replenishment of these cells must take place. Our data suggest that gammadelta T cells in tissues fulfill more than exclusively local functions.

Cellular CD1 proteins bind lipids that differ in length (C(12-80)), including antigens that exceed the capacity of the CD1 groove. This could be accomplished by trimming lipids to a uniform length before loading or by inserting each lipid so that it penetrates the groove to a varying extent. New assays to detect antigen fragments generated within human dendritic cells showed that bacterial antigens remained intact, even after delivery to lysosomes, where control lipids were cleaved. Further, recombinant CD1b proteins could bind and present C(80) lipid antigens using a mechanism that did not involve cellular enzymes or lipid cleavage, but was regulated by pH in the physiologic range. We conclude that endosomal acidification acts directly, rather than through enzymatic trimming, to insert lipids into CD1b. Lipids are loaded in an intact form, so that they likely protrude through a portal near the bottom of the groove, which represents an escape hatch for long lipids from mycobacterial pathogens.

The CD1 family of proteins presents lipid Ags to T cells. Human CD1a, CD1b, and CD1c have been shown in humans to present mycobacterial lipid Ags. Cattle, like humans, are a natural host of several mycobacterial pathogens. In this study, we describe the CD1 family of genes in cattle (Bos taurus) and provide evidence that B. taurus expresses CD1a, CD1e, and multiple CD1b molecules, but no CD1c and CD1d molecules. In mice and humans, CD1d is known to present Ag to NKT cells, a T cell lineage that is characterized by a limited TCR repertoire, capable of rapidly secreting large amounts of IFN-gamma and IL-4. In cattle, two CD1D pseudogenes were found and no intact CD1D genes. Consistent with this, we found complete lack of reactivity to a potent, cross-reactive Ag for NKT cells in mice and humans, alpha-galactosylceramide. Our data suggest the absence of NKT cells in cattle. It remains open whether other cells with the NKT-like phenotype and functions are present in this species. With its functional CD1A and CD1B genes, B. taurus is well equipped to present Ags to CD1-restricted T cells other than NKT cells. Cattle can be used as a model to study group 1 CD1-restricted T cell immunity, including its role in the defense against mycobacterial infections that occur naturally in this species.

The discovery of the CD1 antigen-presenting system reveals that T cells survey the lipid content of target cells via T-cell receptor (TCR) contact with CD1 bound to lipids, glycolipids and small molecules. Recently, CD1 proteins have been found to present mycobacterial lipopeptides that are involved in scavenging iron from infected cells. The mechanism of lipopeptide antigen presentation by CD1 involves the anchoring of antigens in the hydrophobic binding groove, resulting in exposure of the peptide moiety for TCR contact. These findings expand the range of known antigens for T cells and raise the intriguing possibility that CD1, similar to MHC class I and II molecules, enables T cells to discriminate among peptide sequences.

In addition to NK T cells expressing invariant Valpha14 or Valpha24 T cell receptors (TCRs), the CD1d-restricted T cell repertoire is comprised of T cells with diverse TCRs that mediate inflammation during autoimmune and infectious disease. Here we describe the isolation of human Valpha24(-) T cells that are activated by antigen and CD1d. Mass spectrometric and NMR studies revealed that the stimulatory compounds were neither peptidic nor lipidic but instead were composed of sulfur and aromatic hydrocarbon rings, corresponding to the general structure of phenyl pentamethyldihydrobenzofuran sulfonates. Studies of the molecular mechanism of T cell activation showed that a clonotypic Valpha2/Vbeta21 TCR transmitted activating signals, which were highly specific for hydroxylation and methylation patterns at the terminal structures of stimulatory compounds. These studies provide evidence for noninvariant CD1d-restricted T cells in humans and identify the complete molecular structure of a nonlipidic small molecule that activates T cells through an alphabeta TCR.

To seek evidence for a role of molecular mimicry in the induction of Guillain-Barré syndrome (GBS), the authors studied Campylobacter jejuni-reactive T lymphocytes in patients with GBS. In contrast to controls, gammadelta T cells of patients with GBS with antecedent C jejuni infections failed to respond to C jejuni. Supplementing cell cultures with the cytokines interleukin-2 or interleukin-15 resulted in restoration of the gammadelta T cell proliferative response. Gammadelta T cell non-responsiveness may lead to defective regulation of antibody production, and in this way an (auto)immune response against ganglioside-like epitopes on peripheral nerve may cause GBS.

Campylobacter jejuni is the prime cause of foodborne bacterial gastroenteritis. An important complication of C. jejuni enteritis is Guillain-Barré syndrome (GBS), an immune-mediated disorder of the peripheral nerve. The presence of C. jejuni DNA in peripheral blood mononuclear cells (PBMC) of patients with GBS, patients with C. jejuni enteritis, and healthy subjects was studied. Two target genes, the flagellin and the ceuE genes, were used for polymerase chain reaction (PCR) identification of Campylobacter species in DNA extracted from PBMC. Approximately 30% of the healthy subjects and 50% of the patients with GBS had PBMC containing C. jejuni DNA as verified by Southern blot analysis or sequencing of the PCR products. Cell sorting revealed that Campylobacter DNA was present in CD14(+) and CD33(+) populations, indicating that cells from the myelomonocytic lineage are the Campylobacter DNA-carrying cells. These findings show that Campylobacter DNA is present in blood cells of healthy humans, although viable bacteria could not be demonstrated.