No abstract

Summary Cell transmission from mother to offspring was demonstrated using mice with green fluorescent protein (GFP) transgenic markers. GFP transgene heterozygous (+/−) females were mated with GFP (−/−) males, and GFP+ cells in the GFP (−/−) fetuses generated between them were analysed to assess maternal blood cell transmission to conceptuses in utero. The GFP+ maternal cells were observed throughout the body of the fetuses, as shown by fluorescence stereomicroscopy. Cell entrance into the fetal immune system was shown by histochemical and flow cytometric analyses of fetal organs such as thymus, spleen and liver. The GFP+ maternal cells persisted in the offspring until postpartum. Next, GFP (−/−) neonates fed by GFP+ foster mothers were examined to study the transfer of maternal milk leucocytes to offspring through breast‐feeding. GFP+ leucocytes that had infiltrated through the wall of the digestive tract were mainly localized in the livers of neonates. Their accumulation in the livers reached a maximum on days 5 or 6, and these cells became undetectable, as assessed by either histochemistry or flow cytometry, after day 9 of starting foster nursing. Collectively, the present results demonstrate two independent pathways of maternal cell transmission to offspring: transplacental passage during pregnancy and breast‐feeding after birth.

T cells expressing an invariant V(alpha)19-J(alpha)33 T cell receptor alpha-chain (V(alpha)19i TCR) are restricted by the nonpolymorphic major histocompatibility complex class Ib molecule MR1. Whether V(alpha)19i T cells are involved in autoimmunity is not understood. Here we demonstrate that T cells expressing the V(alpha)19i TCR transgene inhibited the induction and progression of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Similarly, EAE was exacerbated in MR1-deficient mice, which lack V(alpha)19i T cells. EAE suppression was accompanied by reduced production of inflammatory mediators and increased secretion of interleukin 10. Interleukin 10 production occurred at least in part through interactions between B cells and V(alpha)19i T cells mediated by the ICOS costimulatory molecule. These results suggest an immunoregulatory function for V(alpha)19i T cells.

T cells expressing an invariant TCR alpha chain and NK cell markers are expected to exhibit unique functions. Whereas much attention has been paid to CD1d-restricted NKT cells, a second NKT cell population bearing an invariant AV19-AJ33 TCR has recently been identified in mice and humans. Selection and/or expansion of this population require B cells, and would involve a non-classical class I-related molecule MR1. Although their preferential distribution in the gut mucosa indicates their role in the host response at the site of pathogen entry, it remains unknown whether they play an alternative role at different sites or in immunological disorders. Using single-strand conformation polymorphism clonotype analysis, we investigated the presence of the human AV19-AJ33 T cells (V(alpha)7.2-J(alpha)33 T cells) in autopsy samples from multiple sclerosis (MS) patients as well as in nerve biopsy samples from chronic inflammatory demyelinating polyneuropathy (CIDP) patients. Here we report that the V(alpha)7.2-J(alpha)33 T cells are accumulated in some of the central nervous system lesions of MS and in the majority of the peripheral nerve samples from CIDP. We have previously revealed that CD1d-restricted, V(alpha)24-J(alpha)Q NKT cells are remarkably reduced in the peripheral blood from MS. However, V(alpha)7.2-J(alpha)33 T cells are not reduced in the peripheral blood from MS and could be detected in a large majority of the cerebrospinal fluid samples obtained during relapse of MS. The present results indicate that the V(alpha)7.2-J(alpha)33 T cells are involved in the autoimmune inflammatory lesions.

A NKT cell repertoire is characterized by the expression of the Valpha19-Jalpha26 invariant TCR alpha chain (Valpha19 NKT cell). This repertoire, as well as a well-established Valpha14-Jalpha281 invariant TCR alpha(+) NKT cell subset (Valpha14 NKT cell), has been suggested to have important roles in the regulation of the immune system and, thus, is a major therapeutic target. Here, we attempted to find specific antigens for Valpha19 NKT cells. Valpha19 as well as Valpha14 NKT cells exhibited reactivity to alpha-galactosyl ceramide (alpha-GalCer). Thus, a series of monoglycosyl ceramides with an axially oriented glycosidic linkage between the sugar and ceramide moiety were synthesized and their antigenicity to Valpha19 NKT cells was determined by measuring their immune responses in culture with glycolipids. Comprehensive examinations revealed substantial antigenic activity for Valpha19 NKT cells by alpha-mannosyl ceramide.

NK1.1+ T cells are an unusual subset of TCR alpha beta cells distinguished by their highly restricted V beta repertoire and predominant usage of an invariant V alpha 14-J alpha 281 chain. To assess whether a directed rearrangement mechanism could be responsible for this invariant alpha chain, we have analyzed V alpha 14 rearrangements by polymerase chain reaction and Southern blot in a panel of cloned T-T hybrids derived from thymic NK1.1+ T cells. As expected a high proportion (17/20) of the hybrids had rearranged V alpha 14 to J alpha 281. However, V alpha 14-J alpha 281 rearrangements always occurred on only one chromosome and were accompanied by other V alpha-J alpha rearrangements (not involving V alpha 14) on the homologous chromosome. These data argue that rigorous ligand selection rather than directed rearrangement is responsible for the high frequency of V alpha 14-J alpha 281 rearrangements in NK1.1+ T cells.

We have demonstrated that analogues of a-mannosyl ceramide (a-ManCer) consisting of a series of immunosuppressive 2-aminoalcohol derivatives in place of sphingosine promote a greater immune response from mouse invariant Va19-Ja26 (AV19-AJ33) TCR-bearing NKT (Va19 NKT) cells than a-ManCer itself. To further characterize the immune responses of Va19 NKT cells to the a-ManCer analogues, cytokine production by the cells was examined in detail. We found that certain a-ManCer derivatives individually induced either Th1-or Th2-dominant cytokine production in culture. The Th1-or Th2-biased immune responses of Va19 NKT cells were dependent on MHC class I-like MR1, since they were induced by coculture with the MR1 transfectants previously loaded with the glycolipids and were inhibited in the presence of anti-MR1 antiserum. Presumably, the recognition of the a-mannosyl residue of the a-ManCer analogues by the invariant TCR is individually modulated, depending on the altered interaction with the groove of the antigen-presenting MR1. Priming of the Va19 invariant TCRtransgenic mice in vivo with these glycolipid derivatives resulted in the induction of the Th1-or Th2-biased immune responses. Thus, these a-ManCer derivatives are likely to be useful in immunotherapy for either Th1 or Th2 excess autoimmune diseases, modulating the function of Va19 NKT cells.

CD1d-deficient (CD1d 3=3 ) mouse lymphocytes were analyzed to classify the natural killer T (NKT) cells without reactivity to CD1d. The cells bearing a VK K19.1^JK K26 (AV19Â J33) invariant TCR K K chain, originally found in the peripheral blood lymphocytes, were demonstrated to be abundant in the NK1.1 þ but not NK1.1 3 T cell population isolated from CD1d 3=3 mice. Moreover, more than half (11/21) of the hybrid cell lines established from CD1d 3=3 NKT cells expressed the VK K19.1^JK K26 invariant TCR K K chain. The expression of the invariant VK K19.1^JK K26 mRNA was absent in L L2-microglobulindeficient mice. Collectively, the present findings suggest the presence of a second NKT cell repertoire characterized by an invariant TCR K K chain (VK K19.1^JK K26) that is selected by an MHC class I-like molecule other than CD1d. ß