Tpre, a new alloantigen encoded in the IgT-C region of chromosome 12, is expressed on bone marrow of nude mice, fetal T cell hybrids, and fetal thymus

Development of Immature CD4+CD8+T Cells Into Mature CD4+ T Cells Requires Alpha-1 Antitrypsin as Observed by Treatment in HIV-1 Infected and Uninfected Controls

Immune cells are, by default, migratory cells that traverse tissue for the purpose of carrying out recognition and recruitment in pathologic inflammation and infection. Members of the LDL receptor family (LDL-RFMs) interact with human leukocyte elastase on the cell surface (HLE-CS) in complex with the abundant blood protein α1proteinase inhibitor (α1PI, α1-antitrypsin, Alpha-1), a process that induces internalization of aggregated functionally-related receptors, including CD4 and the T cell antigen receptor, while simultaneously promoting cellular locomotion. We sought to determine whether augmenting α1PI blood concentration would promote the locomotion of immature T cells through the thymus and generate new CD4⁺ T cells. Two small clinical trials (NCT01370018, NCT01731691, https://clinicaltrials.gov) were conducted in which HIV-1 infected and uninfected individuals were augmented with α1PI and compared with placebo-treated subjects and untreated controls. Blood cell phenotypes were monitored weekly. We found that CD4/CD8 ratio was significantly increased by α1PI augmentation in both uninfected and HIV-1 infected individuals. We found that maturation of CD4⁺CD8⁺ T cells to become immunologically competent CD4⁺ T cells was regulated by α1PI. We propose a strategy targeting HLE-CS for treating secondary immunodeficiency for which there is currently no direct treatment. Treatment to directly elevate T cells in patients with secondary immunodeficiency, including HIV disease, can be provided by alpha-1 antitrypsin augmentation or small molecules that target HLE-CS. Because individuals infected with HIV-1 produce a monoclonal antibody, 3F5, which binds to and inactivates α1PI, a process that prevents α1PI from binding to HLE-CS, thereby blocking locomotion of immature T cells through the thymus to generate CD4⁺ T cells, we further propose that HIV-1 vaccination should include induction of an antibody that binds to and blocks 3F5 activity, thereby preventing AIDS in addition to the current vaccine strategy for preventing HIV-1 infection.

Antigen-specific augmentation factor involved in murine delayed-type footpad reaction. III. Genetic restriction of delayed hypersensitivity augmentation factor (DAF)

We found an antigen-specific factor capable of augmenting delayed-type hypersensitivity (DTH) in the culture supernatant of the mixture of immune T cells and specific antigen, or in the serum of mice immunized with xenogeneic erythrocytes and elicited for DTH footpad reaction. Previous experiments on the genetic restriction of this factor (DTH-augmentation factor; DAF) indicated that DAF activity was effective across the MHC-barrier in C3H/He (H-2k)--BALB/c (H-2d) system. The genetic restriction between DAF and its acceptor cells was then investigated precisely using Igh (immunoglobulin heavy chain locus)-congeneic mice: 1) Expression of DAF activity was MHC-nonrestricted, 2) but was restricted by the Igh-linked gene on the 12th chromosome, 3) such Igh-linked gene restriction was also demonstrated by an absorption test with normal spleen cells. The acceptor cells for DAF were Thy-1+,L3T4+,Lyt-2- T cells.

Rearrangement and expression of T cell antigen receptor and gamma genes during thymic development

Rearrangement and expression of the T cell antigen receptor and the gamma genes during T cell ontogeny is a regulated process; the gamma genes are rearranged and expressed first, followed by the beta and then the alpha genes. Expression of both functional alpha and beta gene RNA first occurs at day 17 of gestation, along with the expression of T3 delta chain RNA. T cell antigen receptor gene rearrangements occur primarily or exclusively in the thymus, although some gamma gene rearrangements occur outside the thymus in fetal liver cells that may be committed T cell progenitors. There is no gross difference in the extent of beta and gamma gene rearrangements in the adult thymocyte subpopulations that were analyzed, despite the fact that some of these populations cannot respond to antigen and never emigrate from the thymus. Quantitative analysis of rearrangements in total adult thymocyte DNA shows that beta gene rearrangements generally occur on both chromosomal homologs, and that rearrangements occur preferentially to the J beta 2 gene segment cluster.

Early events in T lymphocyte genesis in the fetal thymus

There is considerable uncertainty about the nature and level of maturation of the stem cells which colonize the thymus. Arguments are presented here which raise doubts about the claims that these cells have undergone substantial maturation along the T-lineage pathway prior to migration to the thymus. Instead, emphasis is placed on the role of thymic stromal cells in T-lymphocyte maturation. The heterogeneous nature of these cells is well established, but progress is described in analyzing the various cell types and their embryological origins. In particular, the expression of the major histocompatibility complex (MHC) antigens on thymic stromal cells might be relevant to the understanding of restriction and tolerance. The early phases of thymus lymphocyte differentiation are described; but no clear account of the generation of T-cell subsets from immature cells can, as yet, be offered.

H-40, an antigen controlled by an Igh linked gene and recognized by cytotoxic T lymphocytes. I. Genetic analysis of H-40 and distribution of its product on B cell tumors

C.B-20 ( Ighb ) mice challenged with BALB/c ( Igha ) spleen cells (or vice-versa) generate cytotoxic T lymphocytes (CTL) that recognize an antigen, H-40, controlled by an Igh-linked gene. The gene maps to the Igh-C region end of the Igh complex, telomeric to Tsu in the region of Pre-1. At least three alleles, a, b, and c, can be defined. Using a cold target competition assay, no polymorphism of the a allele was detected. Both surface Igh-5a positive and negative spleen cells from (C.B-20 X BALB/c)F1 animals express the a allele of the antigen, indicating that this gene is not allelically excluded. Recognition of the target antigen by CTL is restricted by the D-end of H-2d. The tissue distribution of H-40 was explored using both bulk-cultured and cloned CTL. The antigen is expressed on surface immunoglobulin positive (sIg+) cells and correlates with the expression of sIgM. This was determined by analysis of several B lymphomas as well as of other tumors that varied in their extent of expression of sIg. Four subclones of BCL1 were analyzed. Two of the subclones are sIg+ and express H-40, while two other subclones are sIg- and H-40-. Thus, these data define an Igh-linked gene, separate from immunoglobulin structural loci, that controls an antigen expressed on sIg+ cells. Possible mechanisms to account for this finding are discussed.

Heterogeneity of Igh-linked allotypic determinants expressed on functional T cell subsets as detected by monoclonal antibodies

Hybridomas producing monoclonal antibodies (mAb) specific for immunoglobulin heavy chain (Igh) allotype-linked gene products expressed only on functional T cells but not on B cells and macrophages were established by fusion of allotype congenic SJL (Igh-1b) and SJA /9 (Igh-1a) B cells immunized reciprocally with partner spleen cells with a myeloma P3-X63-Ag8-653 of BALB/c origin. Nine mAb have been selected on the criteria that they can specifically block various antigen-dependent functions of known T cell subsets in in vitro immune responses of mouse strains having the corresponding Igh allotype, but not the other one. These included (a) four mAb that augment the in vitro secondary antibody response of either Igh-1a or Igh-1b strains and thus are considered to react with the Igh-linked allotypic determinant expressed on suppressor T cells, (b) one mAb that inhibits the helper T cell activity of Igh-1b but not of Igh-1a strains, (c) two mAb that inhibit the antigen-induced proliferative response of Igh-1a but not Igh-1b strains, and (d) two mAb that block the cytotoxicity of alloreactive cytotoxic T cells of Igh-1a strains. The linkage to Igh-1 allotype of the T cell products was established by testing with Igh-1-congenic strains with different backgrounds including the H-2 complex. Some of the mAb were able to react with cloned hybridomas and a continuous cell line of the given allotype and functions. Each mAb was able to block one of the known functions of T cell subsets, but not others, indicating the existence of the heterogeneity and multiplicity of the Igh allotype-linked products on T cells.

Genes for the mouse T cell alloantigens Tpre, Tthy, Tind, and Tsu are closely linked near Igh on chromosome 12

Genes encoding the T cell alloantigens Tpre, Tthy, Tind, and Tsu have been mapped to a short segment of chromosome 12 using Igh recombinant strains of mice. These loci are located in a tightly linked cluster between the immunoglobulin heavy chain constant region gene cluster, Igh-C, and the serum prealbumin locus Pre-1, in this manner: centromere--Igh-C--(Tthy, Tind)-Tsu-Tpre--Pre-1.