Nemat Khansari

Phagocytosis of senescent erythrocytes by autologous monocytes: Requirement of membrane-specific autologous IgG for immune elimination of aging red blood cells

The role of membrane-bound IgG present on the membrane of senescent erythrocytes in immune eliminations of aging red cells was investigated. Phagocytosis of populations of red blood cells (RBC) of different ages by autologous monocytes was assessed both by direct phagocytosis and by induction of microsomal heme oxygenase. Removal of IgG from older RBCs inhibited their phagocytosis; in contrast, preincubation of neuraminidase-treated young or in vitro aged RBCs with IgG eluted from old cells led to phagocytosis of RBCs treated by autologous monocytes. It was also found that the Fc portion of membrane-bound IgG is essential for the elimination of senescent cells; less than 15% of old heat-inactivated RBCs coated with F(ab)2 fragment of membrane-bound IgG were phagocytosed. In contrast, more than 50% of old heat-inactivated RBCs coated with heat-eluted IgG were phagocytosed by autologous monocytes. A possible mechanism of elimination of aged cells is discussed.

Immune elimination of autologous senescent erythrocytes by Kupffer cells in vivo

It has been shown previously that autologous monocytes recognize and phagocytose aging self-erythrocytes in vitro. The recognition requires the presence of an autoantibody present in all normal serum. Herein a similar mechanism of recognition and immune elimination of senescent erythrocytes in vivo is reported. When autologous rabbit red blood cells (RBCs), aged either in vivo or neuraminidase-treated young, were reinjected into the animal, most of the old RBCs were trapped in the liver while the majority of the young cells lodged in the spleen. Following reinjection of aging RBCs, the activity of microsomal heme oxygenase enzyme of the liver tissue increased greater than fourfold, suggesting erythrophagocytosis activity of Kupffer cells.

In Vitro Humoral Immune Response of Human Peripheral Blood Lymphocytes to Tetanus Toxoid Sepharose 4B

The in vitro immune response of unfractionated human peripheral blood lymphocytes (PBL) from immune donors who had not been re-immunized with tetanus toxoid (TT) prior to donation was investigated. In this study we were able to stimulate PBL with tetanus toxoid coupled to Sepharose 4B (STT) for production of anti-tetanus toxoid antibody (Ab). Soluble tetanus toxoid or STT alone did not stimulate production of specific Ab. Pokeweed mitogen (PWM) and STT were required for optimal production of IgG and IgM antibodies specific to tetanus toxoid. Specific Ab responses were reduced in low and high concentrations of STT. Depletion of monocytes had no effect on either total IgG or specific IgG synthesis, but decreased the synthesis of both total and specific IgM. Depletion of E-rosette-forming cells decreased the production of specific Ab, suggesting T-dependency of the immune response to STT. Simultaneous production of total immunoglobulin and specific Ab by Sepharose 4B was negligible in the absence of PWM. In the presence of PWM, total immunoglobulin production was optimal, and specific anti-TT Ab production was undetectable. The specificity of the anti-TT Ab was studied by absorption of the culture supernates with an STT column which removed all measurable specific Ab.

Role of autorosette forming cells in antibody synthesis in vitro: Suppressive activity of ARFC in humoral immune response

The role of autologous rosette forming cells (ARFC) in humoral immune responses was studied using an in vitro system. While depletion of ARFCs from PBL resulted in a significant increase of either total IgG or anti-TT IgG, addition of these cells to the system decreased the production of immunoglobulin to a level comparable to that of unfractionated PBL. The majority of the ARFCs reacted with anti-Leu2a and anti-Leu8. In contrast, the majority of non-ARFCs reacted with Leu3a and only 10% with Leu8 monoclonal antibodies. Stimulation of unfractionated PBL with concanavalin A (ConA) resulted in an increase of the ARFC population. ConA stimulation also increased the number of cells reactive with anti-Leu2 and/or anti-Leu8. The autorosette population had a higher purine nucleoside phosphorylase (PNP) content than the non-ARFC population. Although the ARFC suppressed synthesis of antibody by B cell in vitro when they were mixed with either autologous or allogeneic B cells, a marked proliferation of non-B cells was evident. We conclude that at least two different subpopulations of T cells are capable of forming rosettes with autologous red blood cells.

Effects of long-term treatment of mice with anti-I–J monoclonal antibody and dialyzable leukocyte extract on immune function and lifespan

In 1969 Walford hypothesized that age-related dysfunctions of the immune system may be involved in the pathogenesis of the lesions and disease of aging. Studies were initiated to test whether immunologic interventions intended to maintain the integrity of the immune system would delay the onset of diseases of aging and prolong lifespan. Adult BC3F1 mice were treated with anti-I-J monoclonal antibody, with human dialyzable leukocyte extract, or with saline once a week for one year. Spleen cells from the mice were then assayed for suppressor, T-helper and B-cell activity. Treatment with dialyzable leukocyte extract decreased the elevated nonspecific suppressor activity. Mice treated with anti-I-J antibody had elevated T-helper cell activity. In another experiment, mice were treated weekly with anti-I-J antibody, dialyzable leukocyte extract, or saline from 18 months of age until natural death. The mice were immunized with avian gammaglobulin at 27 and again at 29 months of age. Both types of immunologic intervention resulted in a greater secondary antibody response than that of the saline-treated control mice. Mice treated with anti-I-J antibody survived longer than did mice of the other two groups. There was a correlation between the magnitude of the secondary response of individual mice and their lifespan. The results provide support for the immunologic theory of aging.

Specificity of Antigen Induced Helper Factor for Antibody Synthesis In Vitro and its Relation to Lymphocytes Interaction

Human peripheral blood B-cells can be stimulated with PWM and antigen to produce specific antibody in vitro. This stimulation depends on the presence of T-cells and antigen. T cells, however, can be replaced by a soluble factor derived from a 48-hr culture of T-cells with either PWM and/or antigen. The helper factor, in the absence of antigen, acts as a polyclonal activator causing minimal proliferation of B-cells. When antigen is present, production of specific antibody is not dependent on the source of helper factor. Removal of monocytes abolished synthesis of both Ig and specific antibody although antigen and/or helper factor were present. While production of total IgG required autologous monocytes, the origin of the helper factor was not crucial. Production of specific antibody required that both monocytes and helper factor be derived from the same donor; therefore it seems that cooperation of B-, T-cells and monocytes for production of specific antibody is probably Ia restricted. In contrast, for production of polyclonal Ig (in the absence of antigen), cooperation of B-cells and monocytes with T-cells is not.

Implications Involving Autoimmune Mechanisms to the PCP Receptor in Schizophrenia

Substantial evidence indicates that autoimmune mechanisms may either accompany or even precipitate some forms of psychoses. Such findings include: 1. Up to 50% of systemic lupus erythematosus (SLE) patients demonstrate some kind of neuropsychiatric disease; the most commom symptom (psychotic alteration in behavior or thinking) is not due to any known pre-existing psychiatric illness.1 2. The deposition of immune complexes in the choroid plexus is common in such cases and often has been shown to culminate ultimately in both DNA-anti-DNA antibody complexes in the cerebrospinal fluid (CSF)2 and lymphocytic perivascular cuffing of small blood vessels in the frontal cortex and hippocampus.1 Interestingly, although CNS involvement usually develops late in the course of SLE, it often occurs early and can appear as a sporadic disturbance of mental function.3 Thus, evidence exists supporting the concept of altered blood-brain barrier permeability accompanying immune complex disease.1,4 In fact, Rudin has suggested that every SLE patient would develop psychosis if other lethal complications were avoided.5 3. Anti-brain antibodies are commonly detected in SLE and schizophrenia. Bluestein6 reported that 78% of SLE sera contain IgM antineuronal antibody and 17% had IgG antineuronal antibody. Antibrain antibodies have been detected in the sera and sometimes the CSF of 48% of schizophrenics by Pandey and co-workers.7 Others have found 17%, 25%, 21%, 29%, 86%, and 63%8–14 depending on the sensitivity of the test utilized for antibody detection. One of the most interesting studies came from Luria and Domashneva15 in which sera (1:32 dilution) of schizophrenics demonstrated a 100% positive immunofluorescence toward mouse thymocytes in contrast to no reactivity from healthy donors. This finding was later confirmed and extended by Goldstein et al.16

The role of PNP enzyme in autologous rosette-forming cells☆

Since purine nucleoside phosphorylase has been associated with suppressor function in lymphocytes, enzyme activities were studied in autologous rosette-forming cells, a subset showing suppressor properties. Levels of this enzyme were higher in these cells than in other T cells. Con A induction of autologous red cell receptors and suppressor activity of T cells were both inhibited in dose-dependent fashion by Formycin B, a well known inhibitor of purine nucleoside phosphorylase. Inhibition of autologous rosette-forming cells was obtained after pulse treatment of cells with Formycin B for as little as 1 hr, whereas cell proliferation was only inhibited when Formycin B was present throughout culture; this confirms the independence of cell proliferation, and development of red cell receptors and suppressor activity. This study indicates a crucial role for purine nucleoside phosphorylase enzyme in induction of T cell suppressor activity.