Immunoregulation of lysozyme-specific suppression. I. Induction and suppression of delayed-type hypersensitivity to hen egg-white lysozyme

Pharmacological aspects and therapeutic applications of lysozymes

The therapeutic effectiveness of lysozyme (large scale manufactured hen egg-white lysozyme) is actually based on its ability to control the growth of susceptible bacteria and to modulate host immunity against infections and depressions of immune responses. If the former is based on the first evidence of the biological activity of this enzyme, the second is a relatively recent acquisition of extreme importance for the possibilities offered in terms of the regulation of the functioning of the host's immune system. Antibotic activity and immune stimulating effects are also used together, as in the case of the treatment of gastrointestinal infections, including those originated by therapeutical treatments. Based on these biological properties, in addition to the wide range of therapeutic activities for which lysozyme was exploited in the past, at present the most promising data concern the prevention of bacterial cariogenesis and treatment of cancer patients to improve the effectiveness of anticancer drugs or to allow the host to recover from the immune suppression caused by anticancer treatments. However, lysozyme does not yet hold a clear place as an immune modulating agent, in spite of the fact that it has been shown to stimulate immunity with no difference between experimental animals and human beings. The hope is therefore that doctors will understand its potential and that they will take advantage of the existence of this simple and useful molecule.

Immunology of tuberculosis: new directions in research

Tuberculosis is still one of the major health problems in almost all over the world. Thus, new directions in basic and applied research on tuberculosis are under investigation. In this review we have provided recent data obtained in our laboratories on three main aspects of the immunology of tuberculosis, namely: i. the role of B lymphocytes in the processing and presentation of Mycobacterium tuberculosis antigens to T cells; ii. the activation and characterization of mycobacterial-specific T cell clones; iii. the T cell regulation of the immune response to M. tuberculosis. The analysis of the antigenic determinants of M. tuberculosis relevant in the antimycobacterial immunity is the major goal of the WHO programme on the immunology of tuberculosis. In fact, the attempt to develop a second generation vaccine against this microorganism is now possible by analyzing recombinant genomic DNA libraries of M. tuberculosis with monoclonal antibodies and T cell clones. In the near future, the identification of epitopes recognized by mycobacterial-specific T cells with helper, cytotoxic and suppressor functions will allow the preparation of recombinant and synthetic vaccines effective in the control of this disease.

Immunoregulation of lysozyme-specific suppression. III. Epitope-specific amplification of immunosuppression induced by monoclonal suppressor-T-cell products

The hen egg-white lysozyme (HEL)-specific suppression induced by soluble molecules produced by a monoclonal T-cell lymphoma line (LH8-105) obtained from HEL-specific suppressor T lymphocytes has been examined. Injection of I-J+ molecules from LH8-105 cell culture supernatant (TsFa) in HEL-primed mice during the afferent phase of the response induced Lyt-2+ second order suppressor T (Ts) cells which, upon transfer into HEL-CFA-primed syngeneic recipients, inhibit the delayed-type hypersensitivity (DTH) response to HEL. Transfer of spleen cells from TsFa-injected mice primed with HEL or human lysozyme suppresses the DTH response to HEL in recipient mice whereas this response is not affected by cell transfer from ring-necked pheasant egg-white lysozyme (REL)-primed and TsFa-injected mice, indicating that induction of second order Ts by TsFa is specific for a lysozyme epitope including phenylalanine at position 3. Fine antigenic specificity of second order Ts-cell induction is confirmed by similar results obtained upon injection of TsFa in mice primed with HEL N-terminal synthetic peptide or with an analog in which, as in REL, phenylalanine has been substituted by tyrosine at position 3. The same fine antigenic specificity observed in the induction of second order Ts cells is also present in the expression of TsFe suppressive activity. The similar antigenic specificity of Tsa and Tse suggests that Tse cells could result from amplification of the Tsa cell population or these two cell subsets could reflect different maturation stages of the same cell type rather than distinct T-cell populations activated in cascade.

Analysis of lysozyme-specific immune responses by synthetic peptides. I. Characterization of antibody and T cell-mediated responses to the N-terminal peptide of hen egg-white lysozyme

The immunological reactivity against the N-terminal region of hen egg-white lysozyme (HEL) has been investigated by a synthetic peptide (PHEL) comprising residue 1-18 of HEL and by an analogue peptide (PREL) in which phenylalanine at position 3 is substituted by tyrosine. Both peptides are immunogenic in (C57BL/10 X DBA/2)F1 mice genetically responder to HEL. In C57BL/6 mice, genetically nonresponder to HEL, PREL induces anti-peptide antibodies that also bind to PHEL whereas PHEL is not immunogenic. Thus, a single amino acid substitution in a synthetic peptide converts a nonresponder mouse strain into a responder one. Anti-PHEL antibodies demonstrate a higher binding to HEL than anti-PREL antibodies, indicating that phenylalanine at position 3 is important for induction of anti-peptide antibodies able to recognize native HEL. At the T cell level the two peptides show very high bidirectional cross-reactivity between themselves and with HEL for interleukin 2 production, antigen-specific proliferation and delayed-type hypersensitivity response, whereas conservation of phenylalanine at position 3 is required for induction of suppressor cells cross-reactive with HEL. This indicates that the N-terminal region of HEL contains epitope(s) able to induce the same level of helper T cell activity as the native HEL molecule. However, helper T cells do not discriminate between PHEL and PREL whereas phenylalanine at position 3 is critical for HEL-specific suppressor T cell induction.

Immunosuppression by cell-free translation products from monoclonal antigen-specific suppressor T cell mRNA

Polypeptides synthesized in a rabbit reticulocyte lysate system directed by mRNA from the T cell line LH8-105, obtained by radiation leukemia virus-induced transformation of hen egg-white lysozyme (HEL)-specific suppressor T lymphocytes, are able, when injected into mice, to specifically suppress the antibody response and delayed-type hypersensitivity to HEL. The suppressive activity exerted by in vitro translated proteins appears to be independent from post-translational modifications. These in vitro translated polypeptides display fine antigenic specificity in immunosuppression and bind to HEL but not to the closely related ring-necked pheasant egg-white lysozyme immunosorbents. Suppressive molecules obtained by cell-free translation of LH8-105 mRNA or by culture supernatant of LH8-105 cells display, by gel filtration, a similar molecular mass of about 82-90 kDa.

Immunoregulation of lysozyme-specific suppression. II. Hen egg-white lysozyme-specific monoclonal suppressor T cell factor suppresses the afferent phase of delayed-type hypersensitivity and induces second-order suppressor T cells

Culture supernatant from a monoclonal T cell lymphoma line (LH8-105) obtained by radiation leukemia virus-induced transformation of hen egg-white lysozyme (HEL)-specific suppressor T lymphocytes is able, when injected into mice, to specifically suppress the delayed-type hypersensitivity (DTH) reaction induced by HEL. The suppressor T cell factor (TsF) exhibits fine antigenic specificity since it suppresses the DTH response induced by HEL without affecting the DTH response induced by ring-necked pheasant egg-white lysozyme (REL), a lysozyme closely related to HEL. Conversely, LH8-105 TsF is able to suppress the DTH response induced by human lysozyme, distantly related to HEL but sharing a common epitope critical for induction of suppressive activity. The fine antigenic specificity of LH8-105 TsF for a restricted epitope on the HEL molecule is confirmed by binding to HEL but not to REL immunosorbents. This TsF also bears I-J determinants, as demonstrated by binding to monoclonal anti-I-J immunosorbents, and it suppresses the afferent but not the efferent phase of the DTH response to HEL. The afferent suppression is controlled by genes apparently mapping in the I-J subregion of the H-2 complex since I-J-incompatible mice are not suppressed by LH8-105 TsF injection. This inducer-type TsF induces second-order effector suppressor T cells only in HEL-primed mice indicating the primary role of antigen, in association with H-2 (I-J) products, in the afferent portion of this suppressive circuit.