Blocking Activity Of Sera Research Articles

Studies on antilymphocyte antibodies in gestational choriocarcinoma.

The mixed lymphocyte reaction (MLR)-blocking activity of sera was examined in patients with gestational choriocarcinoma. The frequencies of human leukocyte antigens (HLAs) in seven choriocarcinoma patients and their husbands were not different from those in the normal Japanese population. In patients who were successfully treated, many mismatches were found between the woman's HLA-A, B, C antigens and those of her spouse. Sera from three patients showed cytotoxic activity against their husbands' T lymphocytes. Similar results were obtained with sera absorbed with platelets to test for cytotoxic activity against the husbands' B lymphocytes. Cytotoxic activity sometimes disappeared at the recovery stage of the disease. Significant MLR-blocking activity was found in sera of patients in a tumor-bearing stage, but was absent 3-4 months after serum human chorionic gonadotrophin levels dropped into the normal range. It reappeared when patients relapsed, showing that MLR-blocking activity reflected tumor burden. The MLR-blocking factors in patients' sera may not be identical to the so-called serum nonspecific immune inhibitor factors, but was specific to, or dependent on, the use of the husbands' lymphocytes as stimulator cells and was mediated by immunoglobulin (antibodies) reactive with antigens expressed on the husbands' B lymphocytes, e.g. the MHC class II antigens.

Blocking factors in sera of breast cancer patients

In previous studies, we have demonstrated that serum blocking factors (SBF) from sera of breast cancer patients was specific in our Leukocyte Adherence Inhibition assay (LAI).34 To elucidate the nature of SBF, we have investigated the antigen-antibody complex by precipitation of immune complexes (I.C.) with polyethylene glycol (PEG). Specific and nonspecific blocking activities of sera obtained from breast cancer patients were investigated using the LAI and PHA-induced lymphocyte blastogenesis (PHA Blastogenesis) assays. I.C. precipitated in PEG, were utilized to test simultaneously the blocking capacity of these complexes and the corresponding serum. Blocking activity of sera and corresponding I.C. correlated in 20 out of 24 (83%) experiments in the LAI assay and 16 out of 19 (84%) experiments in the PHA Blastogenesis assay. When immune complexes from breast cancer patients were quantitatively compared with normal donors and benign breast patients, a significantly higher yield of protein concentration was obtained. Furthermore, I.C. of benign breast patients was also higher than normal controls. When 10 of the 28 I.C. were further fractionated into Ig (Retentate) and antigen containing component (Filtrate) by ultrafiltration after acid treatment, neither of these components manifested blocking. When reconstituted at a ratio of Ig:antigen = 1:1, blocking activity was again restored in 3 out of 3 in LAI and in 3 out of 4 in blastogenesis. In two experiments, I.C. with negative blocking was readily converted to a positive blocking state with the addition of a small amount of antigen. I.C. also demonstrated specificity in blocking activity and the degree of blocking activity depended on the concentration of I.C. in cultures. Evidence obtained suggests that specific and nonspecific serum blocking factors are related to I.C. but not to the fractionated components of Ig nor antigen. Cancer 43:838–847, 1979.

Naturally occurring lymphocyte-mediated immunity to endogenous type-C virus in the mouse. Blocking of the lymphocyte reactivity with antisera to the virus.

The natural immune response in mice to their endogenous type-C viruses involves a complex interaction between cellular and humoral immune mechanisms. The virus-specific immune reactivities are a function of age and appear only subsequent to endogenous virus expression. Cellular immune activity was found to reside in a population of lymphocytes that were characterized as natural killer cells based on their absence of theta surface antigens or immunoglobulin or complement receptors. Cellular and humoral virus-specific immune responses co-occur in the same animal and pretreatment of virus-positive target cells with sera from virus-positive aging mice is capable of partially blocking the cytotoxic activity of reactive lymphocytes. The blocking activity of sera from individual mice increases as a function of age and endogenous virus expression and is highly correlated with the virus-specific complement-dependent cytotoxic activity of these sera. Mouse sera, whether naturally immune or immune as a result of hyperimmunization with type-C virus, exhibit blocking activity that can be removed by absorption with purified type-C virus or purified viral glycoprotein (gp 70) but not by absorption with noninfected syngeneic cells. High-titered and highly specific antisera directed against certain individual R-MuLV structural proteins reveal blocking activity. Monospecific antisera to gp 70 and p 12 exhibited high-titered blocking reactivities which are absorbable by the respective purified proteins. Blocking activity of antisera directed against other viral structural proteins could not be excluded with certainty. These findings raise the possibility that immunity in the mouse to endogenous type-C virus or virus-infected cells involves competition between serum-blocking activity and natural-killer cell activity and further provides a unique model system for studying the mechanism of action of blocking antisera known to have monospecific reactivity against defined and purifiable transplantation antigens.

In vitro arming and blocking activity of sera from BALB/c mice bearing a spontaneous transplantable adenocarcinoma

The kinetics of the immune response of BALB/c mice to a syngeneic spontaneous adenocarcinoma (ADK- 1t) were analyzed in vitro during the various stages of tumor growth. Cell-mediated cytotoxicity, as measured by a colony inhibition assay, was first detected 5 days after tumor inoculation, reached a peak at about 13 days, and then declined to low but significant levels by day 21. A peak of complement-dependent serum cytotoxicity was observed at 10 days when the tumor size was about 5 mm. Moreover, sera from animals bearing tumors of 1.5–10 mm dia were able to arm lymphocytes from normal BALB/c mice and enhance the cytotoxic activity of lymphocytes from tumor-bearing mice. On the other hand, no blocking activity was observed when the ADK- 1t target cells were preincubated with the same sera. When cytotoxic lymphocytes were pretreated with sera from mice bearing tumors larger than 10 mm in size, inhibition of cell-mediated cytotoxicity was observed. These findings show that the interaction of serum factors on cellular reactivity is of a complex, evolving nature, directly related to the tumor size.

Neural blocking activity of multiple sclerosis and EAE sera.

Neural blocking activity of multiple sclerosis and EAE sera.

Kinetics of serum factors mediating blocking, unblocking and antibody‐dependent cellular cytotoxicity in hamsters given isografts of para‐7 tumor cells

Sera collected at intervals after PARA-7 tumor-cell inoculation were monitored for blocking, unblocking, and antibody-dependent cellular cytotoxicity (ADCC) using the microcytotoxicity test. Within 7 days after isografting, significant levels of blocking were demonstrated. This activity increased in parallel with tumor growth and reached a maximum at day 21. In contrast, the capacity of the sera to mediate ADCC was maximal at day 7, and no longer detectable at 3 weeks. Unblocking was not demonstrable in tumor-bearer sera. Further studies showed that, when the tumor was exicised, blocking activity fell rapidly while ADCC was elevated. Sera collected 7 days after surgery could neutralize the blocking activity of tumor-bearer sera. Significant levels of unblocking were still evident 10 weeks after surgery while ADCC had generally disappeared after 5 weeks. These findings illustrate the complexity of the hamster's humoral immune response to tumor cells, and suggest that (1) the sequestering of antibody by circulating tumor antigen accounts for the demise of ADCC in tumor-bearer sera and the concomitant appearance of blocking activity; and (2) the serum factors mediating ADCC and unblocking differ.

Absorption of blocking activity from human tumor-bearer sera by Staphylococcus aureus, Cowan I.

Staphylococcus aureus, strain Cowan I, contains a cell-wall substance, protein A, which combines with the Fc part of IgG in most mammalian species. It can therefore be used as a solid-phase immunoabsorbant for elimination of the reacting immunoglobulins. Since it has been shown that Cowan I could absorb out the blocking activity of sera from rats bearing isografts of polyoma-virus-induced sarcomas or chemically induced colon carcinomas, we investigated what effects Cowan I absorption of human tumor-bearer sera might have. In all tumor-bearer sera tested, from patients with melanomas or colon carcinomas, treatment with protein-A-containing staphylococci decreased the sera's ability to inhibit lymphocyte-mediated cytotoxicity in vitro. Cowan-I-treated sera from healthy controls had no effect on lymphocyte cytotoxicity. Nor did Cowan-I-treated tumor-bearer sera potentiate or "arm" normal lymphocytes against tumor target cells. There was no evidence of complement-dependent cytotoxicity with added human complement in sera from melanoma and colon carcinoma bearing patients either before or after absorption with Staphylococcus aureus, Cowan I, The concentrations of IgA, IgG and IgM were determined in sera used for in vitro tests of blocking activity and complement-dependent cytotoxicity before and after absorption. No reduction of IgA, reduction to undetectable levels of IgG and 20-30 percent reduction of IgM immunoglobulins as compared to unabsorbed sera were demonstrated.

The effects of cyclophosphamide on in vitro correlates of tumor immunity.

The effects of cyclophosphamide (CY) on tumor immunity against isografts of rat sarcomas induced by polyoma virus were studied using in vitro techniques. Groups of sarcoma-bearing animals received CY (250 mg/kg intraperitoneally 11 days after isografting) CY (150 mg/kg IP 8 days after isografting), or IP injections of 0.9% NaCl. In control rats tumor growth was progressive. All CY-treated animals showed transient tumor regression of at least 50% of their pretreatment tumor volume. Despite a drastic depression in numbers of blood leukocytes as well as lymph-node cells following CY treatment, animals treated with 150 mg/kg CY were shown to have blood lymphocyte and lymph-node cell cytotoxicity in vitro against plated sarcoma target cells comparable to untreated sarcoma-bearing animals. Sera obtained from sracoma-bearing rats prior to CY treatment specifically blocked lymphocyte cytotoxicity against sarcoma target cells. After CY treatment serum blocking activity could not be demonstrated during the period of tumor regression, but reappeared in parallel with tumor regrowth. Antibodies cytotoxic to sarcoma target cells when homologous complement was added could not be demonstrated in sera obtained from animals before CY treatment, but were present after treatment during tumor remission. Following CY treatment, sera obtained from treated animals, when mixed with blocking sera from control animals, could counteract or unblock the blocking activity of tumor-bearer sera. Unblocking capacity was present only in sera obtained during CY-induced tumor remission. Serum IgG concentration was significantly and temporarily decreased after CY treatment.

Embryonic antigens associated with chemically induced colon carcinomas in rats.

AbstractBlood lymphocytes of multiparous, pregnant Wistar/Furth rats were cytotoxic to plated cells derived from chemically induced rat colon carcinomas as well as to fetal kidney, fetal liver and fetal colon cells, but not to normal adult rat colon mucosa cells. Blood lymphocytes and lymph‐node cells from rats bearing colon carcinomas induced by two different chemical carcinogens were consistently cytotoxic to fetal colon cells but never cytotoxic to fetal kidney, fetal liver, or normal adult rat colon mucosa cells. Sera from multiparous, pregnant rats always (4/4 experiments) blocked the cytotoxicity of lymphocytes from colon‐carcinoma‐bearing rats against fetal colon target cells, but less frequently (2/4 tests) inhibited the cytotoxicity of these lymphocytes against colon carcinoma target cells. Sera from colon carcinoma bearers blocked the cytotoxicity of lymphocytes from colon tumor bearers on either colon carcinoma or fetal colon target cells. When assayed with colon carcinoma target cells exposed to lymph‐node cells from colon‐tumor‐bearing rats, the blocking activity of sera from multiparous, pregnant rats could be absorbed out by treatment with colon carcinoma and fetal gut cells, but not by polyoma‐virus‐induced sarcoma, normal colon mucosa, fetal kidney, or whole embryo cells. Blocking activity could be recovered from low pH eluates of the colon carcinoma and fetal gut cells. In 2/3 absorption experiments the ability of sera from multiparous, pregnant rats to block cytotoxicity of lymphocytes from colon tumor bearers incubated with fetal colon target cells was abolished by absorption of the sera with colon carcinoma, fetal gut, fetal kidney and whole embryo cells, but not by absorption with polyoma‐virusinduced sarcoma cells or with normal colon mucosa cells. These results indicate that (1) embryonic antigensgare immunogenic in multiparous, pregnant rats; (2) chemically induced colon carcinomas in rats share at least a partial antigenic identity with a wide spectrum of fetal tissues; and (3) a more particular antigenic cross‐reactivity exists between the colon carcinomas and fetal gut, reflecting the presence of fetal organ‐specific antigens.

Alteration of in vitro anti-tumor activity of tumor-bearer sera by absorption with Staphylococcus aureus, Cowan I.

AbstractStaphylococcus aureus, strain Cowan I, has been shown to contain a cell‐wall substance, protein A, which combines with the Fc part of IgG in most mammalian species. Since the blocking activity of sera from tumor‐bearing individuals has previously been found to be associated with 7S immunoglobulins, it was investigated whether Cowan I could absorb out the blocking activity of sera from rats carrying either isografted polyoma virus induced sarcomas or chemically induced colon carcinomas. In all sera tested, treatment with protein A abrogated the sera's ability to inhibit lymphocyte‐mediated cytotoxicity in vitro. Absorption of sera with Staphylococcus aureus, strain Wood 46, not containing protein A, had no effect on the blocking activity. Admixtures of protein‐A‐treated blocking sera to untreated blocking sera from animals bearing the same tumor type, specifically abrogated the blocking activity, while admixture of Wood 46 absorbed sera, protein‐A‐treated normal sera, or protein‐A‐treated sera from animals bearing a different tumor type did not cause a similar abrogation. The blocking sera from tumor‐bearing rats were not cytotoxic to their specific tumor target cells in the presence of homologous complement. After protein A treatment, serum from rats bearing isografts of sarcomas induced by polyoma virus showed specific complement‐dependent cytotoxicity to polyoma tumor target cells. Serum from primary colon carcinoma bearing rats also had complement‐dependent cytotoxic effect on colon tumor target cells after protein A treatment. Sera used for in vitro tests of blocking activity and complement‐dependent cytotoxicity were analyzed for IgG concentration before and after absorption with S. aureus, Cowan I. A 20‐30% reduction of IgG class immunoglobulins as compared to unabsorbed or control (Wood 46) treated sera was demonstrated.

Further studies on the ability of regressor sera to block cell-mediated destruction of Rous sarcomas.

AbstractPrevious studies have shown that most sera from Japanese quails with growing sarcomas induced by the Schmidt‐Ruppin strain of the Rous virus (SR‐RSV) can block cell‐mediated destruction of Rous sarcoma cells in vitro, and that sera from some quails whose Rous sarcomas have spontaneously regressed (regressors) also have that ability. Six regressor sera, previously shown to be blocking when added to the mixture of target and effector (=regressor spleen) cells in vitro, were tested for blocking effect at either the target or the effector cell level. Three sera could block only when incubated with the target cells, while three other sera blocked at both the target cell and the effector cell level. Two of three regressor sera which had previously been shown to be unblocking (abrogating the blocking activity of progressor sera when mixed with these in vitro) increased cell‐mediated cytotoxicity at a low dilution (potentiation) but had a slight blocking activity at dilution 1:128–1:512, which disappeared upon further dilution. The blocking effect seen at these dilutions appeared to occur at the target cell level and was not detectable after incubation of the effector cells with serum. After incubation of the target cells for 24 h with one of these two regressor sera diluted 1:256, a blocking activity detectable at the effector cell level appeared in the culture medium. The blocking activity of serum from bursectomized progressors (previously reported) increased, after regressor serum diluted 1:16 had been added to it; at that dilution, the regressor serum had no blocking activity by itself. More concentrated regressor serum, on the other hand, was unblocking, i.e. it decreased the blocking activity of serum from bursectomized progressors. The data are compatible with the hypothesis that the blocking factors operating in this system are complexes between antigens released from the tumor and antibodies formed by the host (and, occasionally, free antigen).