Lymphocyte proliferation in vitro induced by hapten autologous protein conjugates. I. A study on the class of lymphocytes responding in vitro and on the nature and specificity of their receptors

Regulator T cells: specific for antigen and/or antigen receptors?

Adaptive immune responses are regulated by many different molecular and cellular effectors. Regulator T cells are coming to their rights again, and these T cells seem to have ordinary alpha/beta T-cell receptors (TCRs) and to develop in the thymus. Autoimmune responses are tightly regulated by such regulatory T cells, a phenomenon which is beneficial to the host in autoimmune situations. However, the regulation of autoimmune responses to tumour cells is harmful to the host, as this regulation delays the defence against the outgrowth of neoplastic cells. In the present review, we discuss whether regulatory T cells are specific for antigen and/or for antigen receptors. Our interest in these phenomena comes from the findings that T cells produce many more TCR-alpha and TCR-beta chains than are necessary for surface membrane expression of TCR-alphabeta heterodimers with CD3 complexes. Excess TCR chains are degraded by the proteasomes, and TCR peptides thus become available to the assembly pathway of major histocompatibility complex class I molecules. Consequently, do T cells express two different identification markers on the cell membrane, the TCR-alphabeta clonotype for recognition by B-cell receptors and clonotypic TCR-alphabeta peptides for recognition by T cells?

Insulin-specific T cell help to TNP-specific B cells requires activation via the antigen T cell receptor

In the present study, the production of large numbers of insulin (Ins)-specific, H-2-restricted T helper (Th) cell clones is described. Among 148 clones analyzed, 121 clones had Th cell function, and these were divided into 75 Ins-specific Th cell clones and 52 autoreactive clones. The 148 clones were isolated from Ins-specific T cell lines produced by in vitro stimulation of T lymphocytes from (b X d)F1 mice immunized with Ins 7, 14, 32 or 56 days before. The following characteristics were tested with regard to the Th cell clones: restriction specificity and antigen requirement for optimal help or interleukin 2 (IL2) production. No differences in these characteristics were found among clones originating from day 7, 14, 32 or 56 T cell lines. A preference for H-2b as restriction element and an antigen concentration of about 0.01 microgram trinitrophenylated (TNP)-Ins/ml for optimal help were general traits. Optimal IL2 release is not yet obtained with 100 micrograms TNP-Ins/ml. Thus, the antigen requirement for optimal help and IL2 release differs by a factor 10(4) at least. Certain twice-cloned Th cell lines were tested for IL2 production when stimulated with anti-Thy-1 monoclonal antibodies (mAb). All clones analyzed were stimulated by mAb H155 but not with mAb H140 nor with mAb against Lyt-1, L3T4, LFA-1 or H-2K/D molecules. Therefore, we determined whether TNP-conjugated H155 mAb would mediate Th cell-B cell collaboration as well as TNP-Ins. The results with nine different Th cell clones and six different TNP-conjugated mAb used in a 10(7)-fold concentration range showed that Th cell clones have to be triggered via the T cell receptor for expression of helper function to B cells. Thus, though IL2 gene activation, synthesis or release apparently can be activated via at least two pathways: T cell receptor or Thy-1, it seems that activation of the genes responsible for synthesis and release of the helper factors, which ensure antigen-specific B cell proliferation and differentiation, needs Th cell-B contact mediated via the antigen-specific T cell receptor.

Antigen-pulsed macrophage monolayers as specific immunoabsorbents: selective absorption of murine T cells committed to soluble protein antigen

Antigen-pulsed macrophage (MO) monolayers in petri dishes were successfully employed as immunoabsorbents, for both the depletion and enrichment of T cells which proliferated upon exposure to soluble ovalbumin (OA). This procedure was shown not to deplete T cells reactive to a second antigen, and similarly MO monolayers pulsed with other antigens failed to deplete the T-cell preparation of OA-reactive cells. Employing brief incubation with trypsin/ethylenediamine tetracetic acid (EDTA), up to 2 X 10(6) OA-binding T cells could be recovered from each petri dish.

Statistical evaluation of the lymphocyte proliferation assay with non-stimulated cultures

A micromethod for the lymphoproliferative assay has been evaluated statistically with non-stimulated human lymphocyte combinations. Different variance components were estimated by means of a hierarchical analysis of variance. Instead of using an arbitrary value for a significant difference between stimulated and non-stimulated cultures, the value can be calculated on the basis of the components of variance in the experimental design. The method disclosed systematic differences between the values of control cultures depending on the lymphocyte combinations and groups of persons examined, which underlines that every experiment should always contain non-stimulated cultures. Further, cell-cell cooperation and differences in spontaneous DNA synthesis within individual lymphocyte populations could be demonstrated.

Colony formation by subpopulations of human T lymphocytes. I. Effects of phytohaemagglutinin and lymphocytosis-promoting factor from Bordetella pertussis

A method is described for the growth in semi-solid agar medium of human lymphocyte colonies in response to stimulation by lymphocytosis-promoting factor (LPF) derived from Bordetella pertussis.

Colony formation was dependent on (a) a liquid pre-culture step with LPF prior to agar seeding, (b) presence of LPF in the agar medium, (c) a cell density in the agar culture of more than 5000 cells per ml.

Optimal colony formation was obtained with 30 μl LPF preparation in the liquid pre-culture step and 20 μl LPF preparation in the agar medium. Moreover, colony development improved after addition of 5 × 10⁻⁵M 2-mercaptoethanol and 0·6% human AB serum. The frequency of LPF-induced T-lymphocyte colonies in ten normal adult donors was 5450±1800 per 10⁶ mononuclear blood cells. In comparison, the frequency of phytohaemagglutinin (PHA)-induced colonies was 20,000±2500 per 10⁶ mononuclear cells plated directly in the agar medium. Lymphocytes seeded in agar medium with LPF started to divide within 2–3 days of culture and formed colonies of 30 to 200 cells on day 7 of culture. Cultures became moribund at day 8. The colony cells were negative for surface immunoglobulin and approximately 75% formed rosettes with sheep red blood cells (SRBC). No synergistic effect between LPF and PHA on colony formation was observed when PHA and LPF were used in the first and second step of culture respectively. Similarly, addition of LPF did not influence the growth of PHA-induced colonies.

When mononuclear cells were depleted of monocytes prior to agar culture addition of supernate factor(s) from cultures of adherent blood mononuclear cells (AC-CM) was necessary to ensure optimal development of colonies.

Mononuclear cells were separated by various rosette-depletion techniques. Colony-forming cells were recovered in the sheep red blood cell-rosetting fraction (E-RFC) of human blood lymphocytes indicating that these precursor cells are themselves T lymphocytes. E-RFCs were separated into Fc(γ)-receptor-positive and negative subpopulations. The frequency of colony-forming cells in the Fc(γ)-receptor-negative T-lymphocyte population was two to ten times higher than that of the Fc(γ)-positive T-cell population. Co-culture of equal numbers of Fc-positive and Fc-negative T lymphocytes reduced the frequency of T colonies by 20 to 95%.

Mononuclear cells were separated by passage through Ig-anti-Ig-coated columns. Attempts to grow LPF-stimulated colonies from passaged lymphocytes failed, suggesting that the colony-forming cells or cells necessary for colony formation were trapped in the column. In contrast, PHA-induced colony formation was enriched in cells which had passed through Ig-anti-Ig-coated columns.

Leukocyte migration inhibition induced by the combination of drug and a liver constituent in patients with drug-induced hepatitis

The leukocyte migration inhibition test in agarose medium was performed in 23 cases of clinically diagnosed drug-induced hepatitis. When the test antigen was the combination of soluble phase of a liver homogenate fractionated by Sephadex G-100 which should have contained liver specific antigen and the offending drug the leukocyte migration was inhibited in 86% of cases. Whereas none of 12 cases of drug allergy without hepatic injury showed a positive result with the same combination of antigens. Other organ homogenate-muscle and kidney-never gave positive results when mixed with the offending drugs in cases of drug-induced hepatitis. It was concluded that in hypersensitivity type drug-induced hepatitis cell-mediated immunity might be established to the complex of liver specific antigen and the drug.

Human leucocyte responses in vitro. I. Transformation of purified T lymphocytes with and without addition of partially purified monocytes

Highly purified Fc receptor-negative T lymphocytes were obtained by filtration of human blood mononuclear cells through Ig–anti-Ig columns. Monocyte-enriched cells were isolated by density centrifugation in bovine serum albumin solutions. The proliferative in vitro response of the purified T lymphocytes was investigated with and without the addition of monocyte-enriched cells, after stimulation by allogeneic cells, phytohaemagglutinin (PHA), pokeweed mitogen (PWM), purified protein derivative (PPD), Candida albicans, Staphylococcus aureus, E. coli and tetanus toxoid.

The results were as follows:

(1) Fc receptor-negative T lymphocytes respond autonomously, and are the main source of proliferative cells found after stimulation by allogeneic cells and optimal doses of PHA, PWM and PPD. Addition of monocyte-enriched cells increases the responses, presumably by a non-specific feeder-effect in the cultures.

(2) Stimulation of Fc receptor-negative T lymphocytes by C. albicans, S. aureus, E. coli and tetanus toxoid requires the presence of autologous monocytes in the cultures, whereas allogeneic monocytes do not support the responses.

(3) Fc receptor-negative T lymphocytes are the main proliferating cells found after stimulation by C. albicans, whereas other cells (B-lymphocytes and/or Fc receptor-positive T lymphocytes) may be responsible for a substantial part of the proliferation elicited by S. aureus, E. coli and tetanus toxoid.

(4) Fc receptor-negative T lymphocytes can stimulate allogeneic cells in mixed lymphocyte culture, but monocyte-enriched cells and unfractionated mononuclear cells are better in this respect.

Antigen specific lymphocyte activity in vitro by peripheral blood leucocytes from Mantoux positive and negative human beings. I. Comparison of quantitative and qualitative differences in the PPD-specific lymphoproliferative response of lymphocytes from the two kinds of donors

Lymphocytes from some PPD (purified protein derivative from tubercle bacillus) skin test negative (Mantoux negative=Mx--) human beings reacted against PPD in the lymphoproliferative assay with a time course and dose response very similar to those of lymphocytes from Mantoux positive (Mx+) individuals. Other Mx-- persons were PPD non-responsive in the lymphoproliferative assay. The PPD response of (immunoglobulin=Ig) Ig anti-Ig column passed lymphocytes (T-cells) from Mx--/LP+ (LP+=lymphoproliferative) persons was significantly reduced whereas the in vitro PPD response of T-lymphocytes from Mx+/LP+ was the same or increased. Purified B-lymphocytes from all kinds of tested individuals did not respond in vitro against PPD. Serological investigations indicated that one of the reasons for the negative skin reaction of individuals whose lymphocytes gave a positive lymphoproliferative response against PPD in vitro, is that such individuals had recirculating PPD of high molecular weight (greater than 900,000) and/or PPD anti-PPD antibody complexes in the serum. These substances could block the PPD-specific T-lymphocytes.

Sequential studies of lymphocyte responsiveness and antibody formation in acute bacterial meningitis

Lymphocyte transformation responses in vitro were studied in eight patients with acute bacterial meningitis (in five due to Neisseria meningitidis). Sequential studies were done from 24--48 hr after the first symptoms of infection to complete recovery. In all cases lymphocyte transformation was depressed during the acute phases of illness. The responses to microbial antigens were more affected than the responses to mitogens. The course of the lymphocyte responses to the causative micro-organism showed no difference from the responses to other microbial species. A moderate shift towards increased sensitivity of the lymphocytes to lower doses of the causative micro-organism was observed during the course of illness in three cases. In N. meningitidis infection, a rapid rise was seen in the serum titres of complement-fixing antibodies and in the number of precipitating antibodies, whereas the rise in immunoglobulin concentrations was more prolonged. Characteristic patterns of elevation and return towards normal were found in the serum concentrations of the acute-phase reactants alpha1-antitrypsin, haptoglobin, and orosomucoid. It is concluded that the lymphocyte transformation responses in vitro during severe bacterial infection are largely governed by non-specific factors, and that studies of lymphocyte responses to micro-organisms should always include other microbial species as controls.

Lymphocyte proliferation in vitro induced by soluble protein antigens. II. Cellular requirements

Immune guinea pig lymph node cells were fractionated on Ig anti-Ig or HSA anti-HSA affinity columns or on plastic surface in medium containing carbonyl iron. These techniques selectively removed B lymphocytes, K lymphocytes or adherent cells. The residual cells (Fc receptor-negative T lymphocytes) responded to soluble antigen in vitro in the same way or even better compared with nonfractionated cells. In addition, there was no indication that antigen-antibody complexes were superior to antigen in triggering lymph node cells or purified lymph code T lymphocytes into DNA synthesis. The results obtained suggested that memory T lymphocytes can be stimulated by antigen autonomously.

Impact of Ig-anti-Ig column fractionation on T-lymphocyte functions

C57Bl/6 anti-Pe15-immune spleen cells were fractionated on immunoglobulin (Ig)-anti-Ig antibody columns in medium containing EDTA or in EDTA-free medium. The antigen-specific cytotoxic potential of immune cells in vitro was only slightly enriched after passage through the columns in the absence of EDTA, whereas immune cells passed through the columns in the presence of EDTA displayed a cytotoxic potential enriched about three times compared with unfractionated cells; this is similar to the enrichment in theta-positive cells. The lack of increase of the cytotoxic potential of immune cells after passage through the columns in the absence of EDTA was shown to be due to the adsorption of subpopulations of cytotoxic T lymphocytes. These cytotoxic cells could be eluted with EDTA-containing medium, and the findings suggest that their adsorption may be mediated via the interaction between cell-bound Fc receptors and the column antigen-antibody complexes.

Rosette-forming ability of thymus-derived lymphocytes in humoral and cell-mediated immunity. II. Helper cell activity

The technique of velocity sedimentation at unit gravity was used to determine the size and rosette-forming ability of helper cells in nonimmune and immune C57BL/6 mice. Helper T cells were assayed by the ability to cooperate with bone barrow (B) cells in the antibody response to sheep erythrocytes (SRBC) in vivo. 19S helper cells in nonimmune animals were nonrosette-forming small lymphocytes; after immunization with SRBC in complete Freund's adjuvant, 19S helper cells were nonrosette-forming medium lymphocytes. 7S helper cells in immune animals were small lymphocytes which did not form rosettes. No SRBC binding by helper cells was observed under the conditions of rosette formation used.