Immunoregulatory function of human cord blood lymphocytes on immunoglobulin production

Spatial proteomics: a powerful discovery tool for cell biology

Protein subcellular localization is tightly controlled and intimately linked to protein function in health and disease. Capturing the spatial proteome - that is, the localizations of proteins and their dynamics at the subcellular level - is therefore essential for a complete understanding of cell biology. Owing to substantial advances in microscopy, mass spectrometry and machine learning applications for data analysis, the field is now mature for proteome-wide investigations of spatial cellular regulation. Studies of the human proteome have begun to reveal a complex architecture, including single-cell variations, dynamic protein translocations, changing interaction networks and proteins localizing to multiple compartments. Furthermore, several studies have successfully harnessed the power of comparative spatial proteomics as a discovery tool to unravel disease mechanisms. We are at the beginning of an era in which spatial proteomics finally integrates with cell biology and medical research, thereby paving the way for unbiased systems-level insights into cellular processes. Here, we discuss current methods for spatial proteomics using imaging or mass spectrometry and specifically highlight global comparative applications. The aim of this Review is to survey the state of the field and also to encourage more cell biologists to apply spatial proteomics approaches.

B cell subpopulations separated by CD27 and crucial collaboration of CD27+ B cells and helper T cells in immunoglobulin production

B cell immunoglobulin production is regulated by helper T cells through direct interaction and secreted cytokines. In the present study, we functionally analyzed CD27 in cord and peripheral blood B cells. Adult peripheral blood B cells were separated into CD27+ and CD27- cells, which differed in their morphology. Cord blood B cells did not express CD27, and CD27 expression on peripheral blood B cells increased with age. Only CD27+ B cells had the ability to produce immunoglobulin, which was increased by contact with a tumor necrosis factor-related transmembrane ligand, CD70. Adult peripheral blood CD27+ B cells can be further subdivided into two discrete subtypes: IgD- CD27+ and IgD+ CD27+ B cells. IgD- CD27+ B cells produce IgG, IgM and IgA, whereas IgD+ CD27+ B cells predominantly produce IgM. The addition of activated CD4+ CD45RO T cells expressing CD70 caused down-regulation of CD27 expression on activated B cells, and this down-modulation was completely blocked by anti-CD70 monoclonal antibody, indicating direct T-B cell contact via CD27/CD70. The triggering via CD27 and CD40 additively increased the immunoglobulin production under Staphylococcus aureus Cowan strain plus interleukin-2 stimulation. Taken together, our findings demonstrate that peripheral blood B cells are separated into subpopulations by CD27 and IgD expression and that CD27+ B cells produce large amounts of immunoglobulin by interaction with the CD70 molecule.

Human cord blood suppressor T lymphocytes. II. Characterization of inducer of suppressor cells

Previously, we reported an antigen nonspecific inducer of T suppressor cell factor (TisF) produced by cord blood mononuclear cells (MNC) in 48-hr, two-way mixed lymphocyte cultures (MLC). The target of this factor was a radiosensitive, T4+ (T8-) adult suppressor T cell subset. The cellular origin of this TisF was examined in the present study. IgG production by pokeweed mitogen (PWM)-stimulated adult MNC was used as an assay for TisF activity. It was found that TisF-producing cells formed rosettes with sheep erythrocytes (E+) and were independent of adherent cells (AC) in the production of TisF. They were resistant to irradiation (2500 rads) and phenotypic characterization with T cell reactive monoclonal antibodies indicated that they resided in the T8- (T4+) population. Furthermore, both TQ1- and TQ1+ cells were required for the production of TisF activity and such activity could not be reconstituted by supernatants from TQ1- MLC and TQ1+ MLC. These results indicate that the production of TisF is dependent upon interactions between radioresistant E+, T8-, TQ1- and radioresistant E+, T8-, TQ1+ cells.

Evaluation of the functional maturity of newborn T8+ suppressor cells and the resistance of newborn lymphocytes to suppression

Concanavalin A (Con A) was used to study the suppressor function of human umbilical cord blood T cells. The suppressor activity and the phenotype of Con A-activated adult and cord T cells were compared using allogeneic adult mononuclear cell (MNC) response to pokeweed mitogen (PWM), phytohemagglutinin (PHA), and alloantigen as indicator culture systems. It was found that Con A-activated adult suppressor T cells were predominantly T8+ cells and suppressed PWM-induced IgG production by adult lymphocytes, as well as PHA- and alloantigen-induced proliferation of allogeneic adult MNC. Con A-activated cord T cells, however, exhibited no significant suppression in any of the three indicator systems. Furthermore, using Con A-activated adult T8+ cells as a source of suppression, the proliferative response of cord lymphocytes to PHA and alloantigen were as susceptible to suppression as those of adult lymphocytes. These results, together with previous findings that PWM-induced cord suppressor T cells were predominantly T4+ cell-mediated suppression, suggest that fetus/newborn lymphocytes achieved their selective inhibition on adult lymphocytes through the T4+ suppressor cell circuit.

Human cord blood suppressor T lymphocytes: I. Phenotype and target of the inducer of suppressor cell factor

The present study examines the characteristics of the cord suppressor T cells and their targets. When an inducer of suppressor T cell factor (TisF) from culture supernatant of alloantigen-activated cord lymphocytes was used as a source of suppression, adult lymphocyte response to soluble antigen candidin, alloantigens, and pokeweed mitogen were all suppressed. These results suggest that TisF acts primarily on T cells in an antigen-nonspecific fashion. Furthermore, preculture T cell irradiation, but not T8+ cell depletion, of adult lymphocytes abrogated the suppressive effect of TisF on the PWM-stimulated IgG production, suggesting that the target of TisF belongs to the radiosensitive T8-(T4+) T cell subset. When different cord T cell subsets were tested for suppressor activity, only radiosensitive T4+ cells were capable of suppressing IgG production by adult lymphocytes. Neither preculture T8+ cell depletion nor irradiation of adult T cells affected the suppression. Taken together, these results suggest that the suppressor activity of cord T cells originated from an inducer of suppressor cells that activates radiosensitive T4+ suppressor effector cells through TisF. In turn, these effector cells act on either radioresistant T4+ helper T cells or B cells or both.