CD69, an 'activation marker' that is rapidly induced on mature T cells after stimulation through the T cell antigen receptor (TCR) was found to be expressed on approximately 10% of normal thymocytes. All of these CD69+ thymocytes express alpha beta TCR, and they include both TCRlowCD4+CD8+ and TCRhighCD4+CD8- or CD4-CD8+ thymocytes. The CD69+ cells can be further segregated into heat-stable antigen (HSA)+TCRlow, HSA+TCRhigh and HSA-TCRhigh thymocyte populations. None of CD69+ cells express the mature T cell marker Qa-2. Thus CD69+ cells present in vivo appear phenotypically to represent transitional cell populations between immature TCRlowHSA+Qa-2-double-positive cells and mature TCRhighHSA-QA-2+ single-positive cells. In addition, TCR engagement by MHC molecules is required for CD69 expression in the thymus. Taken together, the CD69+ thymocytes appear to represent the cells auditioning in positive selection process or they are the cells that have been positively selected recently. Analysis of a TCR transgenic mouse model revealed an increased number of CD69+ thymocytes in a positively selecting thymus, whereas no CD69+ transgenic TCR+ thymocytes were observed in the non-selecting thymus. Based on the results of this study, we suggest that the surface expression of CD69 serves as a useful marker to identify and trace those thymocytes that are engaged in the TCR-mediated positive selection process in the thymus.

The two-dimensional supramolecular structures of a series of N,N'-bis(n-alkyl)naphthalenediimides (NDIs), whose chain lengths span from C3 to C18, at a liquid-HOPG surface interface, studied by STM and FM-AFM, are assigned with the help of molecular dynamics/molecular mechanics calculations to demonstrate that the C3- and C4-NDIs show lamellar structures, the C4- to C12-NDIs show honeycomb (KAGOME) structures, and the C14- to C18-NDIs show lamellar structures again. The change in supramolecular structure depending on chain length can be explained semiquantitatively by the balance of entropy and enthalpy terms to show the importance of "self-avoiding walk" of the alkyl chain in entropy terms.

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A ll jawed vertebrates have two classes of structurally and functionally distinct major histocompatibility complex (MHC) molecules that present peptides to T cell receptors, thereby initiating an adaptive immune response (1). Class I molecules are integral membrane glycoproteins made up of a heavy chain and ␤ 2 -microglobulin that present peptides derived from intracellularly synthesized proteins to CD8 ϩ T cells (2). On the other hand, class II molecules, consisting of two integral membrane glycoproteins designated ␣ and ␤ chains, present peptides produced in or directed to the endosomal͞lysosomal compartment to CD4 ϩ T cells (3). In most animals including human and mouse, class I genes (the genes for the heavy chain of class I molecules) are tightly linked to class II genes (the genes for the ␣ and ␤ chains of class II molecules), collectively forming a gene cluster (1,4,5).Although class I genes that play a major role in antigen presentation map to the MHC, several class I-like genes located outside the MHC have been identified in human and mouse. Examples of such class I-like genes in mice include Cd1 (Cd1d1 and Cd1d2) (6, 7), Azgp1 (the gene for zinc-␣2-glycoprotein) (8, 9), Fcgrt (the gene for the heavy chain of the neonatal IgG Fc receptor) (10, 11), Procr (the gene for the endothelial protein C receptor) (12), H2ls (the gene for the H2 complex class 1-like polypeptide) (13,14), Hfe (the hemochromatosis gene) (15, 16), Raet1a-Raet1e (the genes for retinoic acid early transcripts 1␣-) (17, 18), and H60 (histocompatibility 60) (19). Although these genes have diverse functions, some unrelated to immunity, they all have structural similarities to MHC class I genes and thus qualify as members of the class I gene family.We describe here a family of mouse class I-like genes located outside the MHC. This gene family, which maps to the vicinity of the leukocyte receptor complex (LRC) on chromosome 7, has two members. Interestingly, the proteins encoded by this gene family are related most closely to the MICA͞MICB molecules encoded in the human MHC. After consultation with the International Committee on Standardized Genetic Nomenclature for Mice, we propose to call this newly discovered gene family Mill (MHC class I-like located near the LRC) and its two members Mill1 and Mill2. Materials and MethodsIsolation of Mill1 and Mill2 cDNA by RT-PCRs. A computer search of the mouse EST section of the GenBank database resulted in the identification of three clones predicted to encode two distinct, class I heavy chain-like molecules. Based on the sequences of these clones, we designed primers that enabled the isolation of full coding sequences of Mill1 and Mill2 cDNA. The primer sequences were 5Ј-TGGCTTGGGATCTTCAAAGT-3Ј (sense) and 5Ј-TCCTCTGTCTTGTTTGGCTGTT-3Ј (antisense) for Mill1 and 5Ј-TTTGCACAAAACTCCATTTGA-3Ј (sense) and 5Ј-AGAAACAGCCAAGCCTCAGTC-3Ј (antisense) for Mill2. The cDNA templates for PCR were synthesized as described (20) by using total cellular RNAs isolated from the skin of 1-day-old BALB͞cCrSlc mice (Mill1)...

Three manganese(II) complexes, [Mn(II)(2)L(1)(2)(H(2)O)(4)](ClO(4))(2).H(2)O (1, L(1)H = (bis(2-pyridylmethyl)amino)acetic acid), [Mn(II)(2)L(2)(2)(H(2)O)(2)](BPh(4))(2).2EtOH.2H(2)O (2, L(2)H = 3-(bis(2-pyridylmethyl)amino)propionic acid), {[Mn(II)(2)L(2)(2)(H(2)O)(MeCN)](BPh(4))(2).2MeCN}(infinity) (3), and a manganese(IV) complex [Mn(IV)(2)O(2)L(2)(2)](ClO(4))(2).4H(2)O (4) were synthesized and characterized by X-ray crystallography. The compound 1 was a dinuclear Mn(II)(2) complex which crystallized in the monoclinic crystal system, space group P2(1)/n, with Z = 4, a = 12.19(1) Å, b = 14.623(8) Å, c = 21.72(1) Å, beta = 96.29(6) degrees, V = 3849(4) Å(3). The complex cation had an approximate C(2) symmtery. The two manganeses were both seven-coordinate and doubly bridged by one oxygen atom of carboxylate groups in &mgr;(2),eta(1)-mode. The compound 2 was also a dinuclear Mn(II)(2) complex which crystallized in the monoclinic crystal system, space group P2(1)/n, with Z = 2, a = 16.760(2) Å, b = 9.643(2) Å, c = 23.533(2) Å, beta = 92.984(8) degrees, V = 3798.4(7) Å(3). The complex cation of 2 also had two seven-coordinate manganese ions, but unlike 1 the nonbridging carboxylate oxygens weakly coordinate to the manganese ions. The compound 3 crystallized in the orthorhombic crystal system, space group P2(1)2(1)2(1), with Z = 4, a = 27.888(3) Å, b = 29.054(2) Å, c = 9.428(2) Å, V = 7638(2) Å(3). The cationic portion of 3 consisted of infinite chains of Mn(II) (two Mn(II) ions per an asymmetric unit) bridged by carboxylates in bidentate syn/anti mode. The compound 4 was a dinuclear bis(&mgr;-oxo) Mn(IV)(2) complex which crystallized in the trigonal crystal system, space group R&thremacr;, with Z = 8, a = 23.962(4) Å, c = 17.190(3) Å, V = 8547(3) Å(3). All these structures are made up from a common fragment "L(n)()Mn" assembling in various topologies. Variable-temperature magnetic susceptibility measurements revealed that the Mn(II) ions in 1-3 were weakly antiferromagnetically coupled (J = -0.631(6), -0.655(5), and -0.20(1) cm(-)(1) for 1-3), and that the Mn(IV) ions in 4 were strongly antiferromagnetically coupled (J = -97.5(5) cm(-)(1)). The cyclic voltammogram of 4 showed two reduction waves with E(1/2) values of -0.52 and 0.28 V (vs ferrocene). These E(1/2) values are more negative by 0.1 V than those of the closely related complex [Mn(III)Mn(IV)O(2)L(1)(2)](ClO(4)).