Lymphotactin

Lymphotactin Daniel J. Catron and Albert Zlotnik* Department of Immunobiology, DNAX Research Institute of Molecular and Cellular Biology, Inc., 901 California Avenue, Palo Alto, CA 94304-1104, USA * corresponding author tel: (650) 496-1131, fax: (650) 496-1200, e-mail: [email protected] DOI: 10.1006/rwcy.2000.11020.

SUMMARY Lymphotactin is the only member of the C or class of chemokines due to the absence of two of the characteristic four cysteines normally found in the chemokine superfamily. In humans, there are two forms, called XCL1 and XCL2, which are the products of two closely related genes. Lymphotactin is found on chromosome 1 in both humans and mice. Lymphotactin is a potent T and NK cell chemoattractant. It is a major product of CD8+ T cells, with NKT cells and NK cells, TH1 CD4+ T cells, mast cells, and  T cells also producing it to a lesser degree. Lymphotactin is produced upon T or NK cell activation. Its production can be induced in vitro by T cell mitogens and in vivo during the course of an antigen-specific immune response. IL-10 inhibits its production indirectly by acting on the antigenpresenting cells. The lymphotactin receptor is XCR1 (formerly known as GPR5).

BACKGROUND Lymphotactin (Lptn) is a unique chemokine that has lost two of the characteristic four cysteines typical of the chemokine superfamily (Kelner et al., 1994; Yoshida et al., 1996). As such, it has lost one of the two disulfide bonds that maintain the structure of most chemokines. At the time it was initially described, it was shown that its gene was located in mouse chromosome 1 (Kelner et al., 1994), while the genes encoding human lymphotactin are in the syntenic region in human chromosome 1 as well (Kennedy et al., 1995). Taken together, these characteristics suggest that lymphotactin represents a third kind of chemokine different from either the CXC or CC

subfamilies, and has been called the C or class of chemokine.

Discovery Lymphotactin was discovered while screening a cDNA library of activated CD44+CD25+CD4ÿ D8ÿ CD3ÿ (triple negative) pro-thymocytes which were subtracted from a cDNA library of resting pro-thymocytes.

Alternative names Lymphotactin has also been described as singlecysteine motif chemokine (SCM-1 and -2) as well as an activation-induced, chemokine-related molecule expressed in CD8+ T cells (Mueller et al., 1995). According to the new chemokine nomenclature, human lymphotactin  and , which differ by two amino acids, will be called XCL1 and XCL2 respectively (two products of closely related human genes).

Structure No structural studies have been reported on lymphotactin.

Main activities and pathophysiological roles Lymphotactin is a potent T and NK cell chemoattractant, both in vitro and in vivo (Giancarlo et al., 1996; Hedrick et al., 1997).

1290 Daniel J. Catron and Albert Zlotnik

GENE AND GENE REGULATION

Description of protein

Accession numbers

No structural features known yet. A long C-terminus tail is necessary for functional activity.

Mouse lymphotactin: U15607 Human lymphotactin: (a) Lymphotactin  U23772; same as SCM-1 precursor D63790. This form is now designated XCL1. (b) Lymphotactin ; same as SCM1 precursor D63789. This form is now designated XCL2. The two forms of human lymphotactin differ in two amino acid substitutions (HR instead of DK) shortly before the first cysteine (see the underlined amino acids in Figure 1).

Chromosome location Both the mouse gene (Kelner et al., 1994) and the human gene (Kennedy et al., 1995) encoding lymphotactin are located in chromosome 1.

Cells and tissues that express the gene See Cellular sources that produce.

Accession numbers See the gene accession numbers above.

See Figure 1.

No crystal structure known yet.

Important homologies Shares various degrees of homology with a number of CC chemokines.

Posttranslational modifications Lymphotactin is glycosylated in its native form, but it is currently unknown if glycosylation affects the activity of the protein.

CELLULAR SOURCES AND TISSUE EXPRESSION

Cellular sources that produce

PROTEIN

Sequence

Discussion of crystal structure

Most lymphoid tissues are positive for lymphotactin mRNA. Lymphotactin is a major product of activated CD8+ T cells (Kelner et al., 1994; Kelner and Zlotnik, 1995; Mueller et al., 1995). Other producing cells include NKT cells and NK cells (Hedrick et al., 1997). For this reason, lymphotactin production appears to be linked to class I MHC-restricted T cells. However, it is also produced by TH1 CD4+ T cells (Bradley et al., 1999), mast cells (Rumsaeng et al.,

Figure 1 Amino acid sequences for human lymphotactin , human lymphotactin , and mouse lymphotactin.

Lymphotactin 1291 1997), and  epidermal T cells (Boismenu et al., 1996).

Eliciting and inhibitory stimuli, including exogenous and endogenous modulators Produced upon T or NK cell activation. Any T cell mitogens would induce it and it is also made in the course of antigen-specific immune responses. Presumably IL-10 inhibits its production indirectly by acting on the antigen-presenting cell.

RECEPTOR UTILIZATION The lymphotactin receptor has been identified as the former orphan receptor GPR5 (Yoshida et al., 1998). In general, the expression pattern correlates with the known functional abilities of lymphotactin, with the exception of a surprising expression in placenta. However, it is not known which cell type expresses the lymphotactin receptor (now renamed XCR1) in placenta, although one possibility is that NK cells are present in that organ.

IN VITRO ACTIVITIES

In vitro findings Chemoattracts T cells and NK cells in vitro.

Bioassays used Boyden chamber and chemotaxis transwell assays.

IN VIVO BIOLOGICAL ACTIVITIES OF LIGANDS IN ANIMAL MODELS

Normal physiological roles Possibly chemoattracts T and NK subsets in vivo.

Species differences In the human, there are two lymphotactin genes (Yoshida et al., 1996) differing for two amino acids.

It is presently unclear whether both are expressed. All ESTs present in the public database actually correspond to only one form. In the mouse, only one gene has been identified. We recently identified a gene that is likely to represent chicken lymphotactin (Rossi, 1999), although the protein attracts B cells better than T cells.

PATHOPHYSIOLOGICAL ROLES IN NORMAL HUMANS AND DISEASE STATES AND DIAGNOSTIC UTILITY

Normal levels and effects Unknown; probably no detectable levels. Produced only under T cell activation. May be present in the placenta.

Role in experiments of nature and disease states Probably an important recruiter of T cells during infections dependent on class I MHC-restricted responses (i.e. viral infections).

IN THERAPY

Preclinical: How does it affect disease models in animals? Lymphotactin has been shown to synergize with IL-2 in inducing antitumor immunity in mice in vivo to protect against challenge with B cell lymphoma A20 tumor cells (Dilloo et al., 1996). Presumably, it acts by recruiting T and NK cells to the tumor developing site and IL-2 activates the recruited cells to attack the tumor. Lymphotactin has also been reported to enhance the antitumor effects of dendritic cells when these are transfected with lymphotactin prior to being injected in vivo to enhance antitumor immunity (Cao et al., 1998; Zhang et al., 1999). Other activities of lymphotactin include adjuvant activity in mucosal responses (Lillard et al., 1999). When lymphotactin was given intranasally along with antigen to mice, it enhanced the number of antigen-specific, antibodyforming cells in both mucosal and systemic compartments. Mucosal T cells also display a higher proliferate ability to their specific antigen when challenged in vitro.

1292 Daniel J. Catron and Albert Zlotnik The connection with class I MHC-restricted T cells mentioned earlier suggests that lymphotactin may also play a role in early graft rejection. In fact, Wang et al. (1998) have suggested that lymphotactin is a key regulator of lymphocyte trafficking during graft rejection. Less is known about a role for lymphotactin in autoimmune diseases. Natori et al. (1998) have studied the expression of lymphotactin in an animal model of experimental crescentic glomerulonephritis and found a strong correlation between lymphotactin mRNA expression and an influx of CD8+ T cells. These observations strongly suggest a role for lymphotactin in the recruitment of leukocytes during autoimmunity.

Effects of therapy: Cytokine, antibody to cytokine inhibitors, etc. The effects reported in vivo used a gene therapy approach. No studies using recombinant protein have been reported so far.

References Boismenu, R., Feng, L., Xia, Y. Y., Chang, J. C., and Havran, W. L. (1996). Chemokine expression by intraepithelial gamma delta T cells. Implications for the recruitment of inflammatory cells to damaged epithelia. J. Immunol. 157, 985±992. Bradley, L. M., Asensio, V. C., Schioetz, L. K., Harbertson, J., Krahl, T., Patstone, G., Woolf, N., Campbell, I. L., and Sarvetnick, N. (1999). Islet-specific Th1, but not Th2, cells secrete multiple chemokines and promote rapid induction of autoimmune diabetes. J. Immunol. 162, 2511±2520. Cao, X., Zhang, W., He, L., Xie, Z., Ma, S., Tao, Q., Yu, Y., Hamada, H., and Wang, J. (1998). Lymphotactin gene-modified bone marrow dendritic cells act as more potent adjuvants for peptide delivery to induce specific antitumor immunity. J. Immunol. 161, 6238±6244. Dilloo, D., Bacon, K., Holden, W., Zhong, W., Burdach, S., Zlotnik, A., and Brenner, M. (1996). Combined chemokine and cytokine gene transfer enhances autitumor immunity. Nature Med. 2, 1090±1095. Giancarlo, B., Silvano, S., Albert, Z., Mantovani, A., and Allavena, P. (1996). Migratory response of human natural killer cells to lymphotactin. Eur. J. Immunol. 26, 3238±3241.

Hedrick, J. A., Saylor, V., Figueroa, D., Mizoue, L., Xu, Y., Menon, S., Abrams, J., Handel, T., and Zlotnik, A. (1997). Lymphotactin is producted by NK cells and attracts both NK cells and T cells in vivo. J. Immunol. 158, 1533±1540. Kelner, G. S., and Zlotnik, A. (1995). Cytokine production profile of early thymocytes and the characterization of a new class of chemokine. J. Leukoc. Biol. 57, 778±781. Kelner, G. S., Kennedy, J., Bacon, K. B., Kleyensteuber, S., Largaespada, D. A., Jenkins, N. A., Copeland, N. G., Bazan, J. F., Moore, K. W., and Schall, T. J. (1994). Lymphotactin: a cytokine that represents a new class of chemokine. Science 266, 1395±1399. Kennedy, J., Kelner, G. S., Kleyensteuber, S., Schall, T. J., Weiss, M. C., Yssel, H., Schneider, P. V., Cocks, B. G., Bacon, K. B., and Zlotnik, A. (1995). Molecular cloning and functional characterization of human lymphotactin. J. Immunol. 155, 203±209. Lillard, J. W., Jr., Boyaka, P. N., Hedrick, J. A., Zlotnik, A., and McGhee, J. R. (1999). Lymphotactin acts as an innate mucosal adjuvant. J. Immunol. 162, 1959±1965. Mueller, S., Dorner, B., Korthauer, U., Mages, H. W., D'Apuzzo, M., Senger, G., and Kroczek, R. A. (1995). Cloning of ATAC, an activation-induced, chemokine-related molecule exclusively expressed in CD8+ T lymphocytes. Eur. J. Immunol. 25, 1744±1748. Natori, Y., Ou, Z. L., Yamamoto-Shuda, Y., and Natori, Y. (1998). Expression of lymphotactin mRNA in experimental crescentic glomerulonephritis. Clin. Exp. Immunol. 113, 265± 268. Rossi, D., Sanchez-Garcia, J., McCormack, W. T., Bazan, J. F., and Zlotnik, A. (1999). Identification of a chicken ``C'' chemokine related to lymphotactin. J. Leukoc. Biol. 65, 87±93. Rumsaeng, V., Vliagoftis, H., Oh, C. K., and Metcalfe, D. D. (1997). Lymphotactin gene expression in mast cells following Fc(epsilon) receptor I aggregation: modulation by TGF-beta, IL-4, dexamethasone, and cyclosporin A. J. Immunol. 158, 1353±1360. Wang, J. D., Nonomura, N., Takahara, S., Li, B. S., Azuma, H., Ichimaru, N., Kokado, Y., Matsumiya, K., Miki, T., Suzuki, S., and Okuyama, A. (1998). Lymphotactin: a key regulator of lymphocyte trafficking during acute graft rejection. Immunology 95, 56±61. Yoshida, T., Imai, T., Takagi, S., Nishimura, M., Ishikawa, I., Yaoi, T., and Yoshie, O. (1996). Structure and expression of two highly related genes encoding SCM-1/human lymphotactin. FEBS Lett. 395, 82±88. Yoshida, T., Imai, T., Kakizaki, M., Nishimura, M., Takagi, S., and Yoshie, O. (1998). Identification of single C motif-1/lymphotactin receptor XCR1. J. Biol. Chem. 273, 16551±16554. Zhang, W., He, L., Yuan, Z., Xie, Z., Wang, J., Hamada, H., and Cao, X. (1999). Enhanced therapeutic efficacy of tumor RNApulsed dendritic cells after genetic modification with lymphotactin. Hum. Gene Ther. 10, 1151±1161.