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Biomedical subjects

A A Vandenbark

Publications and source records attributed to A A Vandenbark.

18 recordsLinked to original sources
PubMed1979

The role of 5'-methylthioadenosine phosphorylase in 5'-methylthioadenosine-mediated inhibition of lymphocyte transformation.

To determine if increased 5'-methylthioadenosine phosphorylase activity in activated lymphocytes may be responsible for the decreased inhibitory effect noted when 5'-methylthioadenosine is added after stimulation, the activity of this enzyme was monitored during lymphocyte transformation. A direct correlation existed between the transformation process and 5'-methylthioadenosine phosphorylase activity; the longer the stimulation process progressed, the phosphorylase activity; the longer the stimulation process progressed, the greater the enzyme activity. The 7-deaza analog of 5'-methylthioadenosine, 5'-methylthiotubercidin, was utilized to explore further the role that the phosphorylase may play in the reversal process. 5'-Methylthiotubercidin acted as a potent inhibitor, but not a substrate, of the 5'-methylthioadenosine phosphorylase, and was an even more potent inhibitor of lymphocyte transformation than 5'-methylthioadenosine. However, in direct contrast to the 5'-methylthioadenosine effect, inhibition by 5'-methylthiotubercidin could not be completely reversed. These data suggest the 5'-methylthioadenosine phosphorylase plays an important role in reversing 5'-methylthioadenosine-mediated inhibition and that the potent, nonreversible inhibitory effects of 5'-methylthiotubercidin are due to its resistance to 5'-methylthioadenosine phosphorylase degradation.

Adenosine↗
PubMed1979

Myelin basic protein binding cells in active multiple sclerosis.

A sensitive, antigen-specific rosetting technique was used to enumerate blood cells that bind myelin basic protein (BP) in MS patients and controls. Sixteen of 23 MS patients in exacerbation but only 7 of 48 in remission formed elevated numbers of rosettes. Five of the latter 7 patients had recovered from an exacerbation within four months of the laboratory evaluation. Eight of 20 patients with progressive MS, all of whom had had disease for more than four years, had BP rosette-forming cells. None of the 16 normal volunteers and 1 of 8 neurological controls had BP rosette-forming cells. These results suggest that BP-binding cells in MS are confined to patients in acute exacerbation or within four months of activity, and those who have had progressive disease for at least four years.

Antigen-Antibody Reactions↗
PubMed1979

Immune response to melanoma extracts in three melanoma-prone families.

Immune reactivity to melanoma extracts was measured by the leukocyte adherence inhibition (LAI) test in 40 members of 3 melanoma-prone families. The melanoma patients had a wide range of responsiveness to the extract, the highest responder being a 10-year survivor. As a group, family members (including spouses) without disease had significantly elevated LAI responses compared to those of unrelated controls (P less than 0.01). Within the families, members with close exposure to melanoma patients for 10 years or more had a significantly higher response to melanoma antigen than did members with 0-5 years of close exposure (P less than 0.05). Responses of spouses and members at high risk of developing melanoma (B-K mole syndrome) also correlated with length of exposure to patients, which suggests that the elevated LAI response was not genetically determined. The high frequency of positive responses to melanoma antigens in these families, particularly in spouses, suggests the presence of transmissible melanoma-associated material capable of immunizing persons in contact with melanoma patients.

Antigens, Neoplasm↗
PubMed1979

Assessment of the mechanism of the leukocyte adherence inhibition test.

This study was designed to elucidate the mechanism of the leukocyte adherence inhibition (LAI) test in man. To identify the reactive cell types, enriched leukocyte populations (dextran-separated leukocytes and Hypaque-Ficoll-isolated mononuclear cells and neutrophils, as well as rosette-isolated B- and T-lymphocytes) were tested for leukocyte adherence in the absence of serum to tumor-specific antigens. LAI reactivity was not restricted to any of the enriched populations, suggesting the involvement of multiple cell types. Attempts to demonstrate soluble lymphocyte factors in the LAI mechanism have been uniformly negative. In contrast, factors in serum of immune donors were able to arm naive cells to be specifically responsive. This suggests a role for serum factors in the mechanism of LAI reactivity and partially explains the participation of multiple cell types in the responses observed. In additional studies, we could not document a correlation between the magnitude of the dermal test (delayed cutaneous hypersensitivity) and the magnitude of the LAI response in patients with squamous cell carcinoma of the head and neck. In 34 of 54 of these patients, there was agreement between the two tests (both positive, 27 of 54; both negative, 7 of 54). In the remaining 20 patients, the dermal test was greater than 5 mm while the LAI test was negative (less than 30% inhibition).

Antibodies, Neoplasm↗
PubMed1979

Human transfer factors: structural properties suggested by HPRP chromatography and enzymatic sensitivities.

Leukocyte extracts containing human transfer factor (TF) were fractionated by exclusion chromatography, and the active fraction (Sephadex G25, Fraction IIIa) was subjected to high pressure, reverse phase (HPRP) chromatography and enzymatic degradation. TF activity was assessed by the systemic transfer of dermal skin test reactivity from KLH-immunized donors to naive recipients. Preparative HPRP chromatography resolved Fraction IIIa into multiple chromophoric regions, two of which demonstrated transfer of KLH reactivity. Alkaline phosphatase treatment of Fraction IIIa converted the major ultraviolet-absorbing component, 5'-inosine monophosphate, to inosine and resulted in TF activity being restricted to one region. This HPRP region (R1A) contained less than 1% of the UV254 active material in Fraction IIIa but greater than 90% of the reactivity. The sensitivity of TF to pronase, proteinase K, phosphodiesterase I, and phosphodiesterase II was evaluated by inhibition of systemic transfer of KLH reactivity. Pronase and proteinase K destroyed systemic transfer activity and the pronase destruction could be inhibited with traysylol. Phosphodiesterase I, a 3' exonuclease, destroyed activity, whereas phosphodiesterase II, a 5' exonuclease, did not. The data are consistent with a phosphodiester-containing polypeptide in the structure of human TF for KLH reactivity.

Alkaline Phosphatase↗
PubMed1979

Association of melanoma tumor antigen activity with beta2-microglobulin.

The majority of melanoma tumor antigen activity present in melanoma extracts derived from fresh tumor tissue binds to a Sepharose-anti-beta2-microglobulin adsorbent. Removal of HLA antigens from the extracts of melanoma tissue by using a KBr flotation technique did not reduce either the tumor antigen activity of the extracts or the binding of melanoma tumor antigen (MTA) activity to the Sepharose-anti-beta2-microglobulin adsorbent. The complete blocking of MTA activity by pretreating the anti-beta2-microglobulin adsorbent with beta2-microglobulin and the lack of detectable MTA binding to a Sepharose anti-normal human serum adsorbent demonstrated the specificity of the binding of MTA to the anti-beta2-microglobulin adsorbent.

Antigens, Neoplasm↗
PubMed1978

Changes in tumor immunity during therapy determined by leukocyte adherence inhibition and dermal testing.

Leukocyte adherence inhibition (LAI) is an easily carried out in vitro test for tumor reactivity which is based on the prevention of adherence of leukocytes incubated with antigen to which the donor is immune. In this study a comparison is made with dermal response to tumor antigen. A total of 234 patients were tested, 74 of whom had melanoma, 111 of whom had squamous cell carcinoma of the head and neck, 18 of whom had neuroblastoma and 31 of whom had other tumors. Forty-two persons without tumors acted as controls for the LAI test. A high degree of correlation was found between LAI and dermal response. Furthermore, LAI exhibited marked tumor specificity and showed a ten-fold greater sensitivity than dermal response. LAI may be used to monitor serial changes in tumor reactivity in cancer patients.

Adolescent↗
PubMed1977

Human transfer factor: fractionation by electrofocusing and high pressure, reverse phase chromatography.

The biologically active fraction of human transfer factor (Sephadex G-25, fraction III) has been separated by exclusion chromatography into two component fractions (IIIa and IIIb). Fraction IIIa transferred donor reactivities to PPD or KLH into 9 of 9 recipients. Fraction IIIb did not transfer donor reactivities (0 of 8 transfers) but did produce both antigen-independent and antigen-dependent dermal reactions in recipients. Fractionation by electrofocusing and high pressure reverse phase chromatography revealed that IIIa has a major UV254 absorbing component and that fraction IIIb has at least three major and three minor UV absorbing components. The major component of IIIa was isolated by preparative electrofocusing, had an isoelectric point of 1.6, and transferred KLH reactivity to four of five recipients.

Chemical Fractionation↗
PubMed1976

Human transfer factor: fractionation and biologic activity.

Human transfer factor (TF) was fractionated by exclusion chromatography and the fractions were tested for biologic activity in vivo and in vitro. Specific TF activity in vivo was found to reside in the major UV-absorbing peak (Fraction III). Fraction III eluted at 2.7 X V(O) and transferred tuberculin, candida, or KLH-reactivity to previously negative recipients. Fraction III from nonreactive donors was ineffective. When the fractions were tested in vitro, we found that both the mitogenic activity of whole TF and the suppressive activity to mitogen activation when present in TF was found in Fraction I. Fraction III contained components responsible for augmentation of PHA and PWM responses. In addition, Fraction III contained the component responsible for antigen-dependent augmentation of lymphocyte transformation. Fraction IV was suppressive to antigen-induced lymphocyte transformation. These data suggest that TF preparations contain components which can affect immune reactions in both specific and nonspecific ways.

Antigens↗
PubMed1976

Nicotinamide: suppression of lymphocyte transformation with a component identified in human transfer factor.

The component in human transfer factor (TF) (Fraction IV, from exclusion chromatography on Sephadex G-25) responsible for suppression of antigen-induced lymphocyte transformation was previously identified as nicotinamide. Commercially available nicotinamide was subsequently shown to produce suppression of antigen-induced responses in vitro previously observed with TF Fraction IV. Nicotinamide was found to be nontoxic at the highest concentrations employed (10(-2)M) and suppressive over a relatively broad range (10(-5) to 10(-2)M. The suppression appeared to be related to the magnitude of antigen- or mitogen-induced transformation and was apparent even when nicotinamide was added as late as 48 hr after stimulant addition.

Antigens↗
PubMed1976

Human transfer factor: effects on lymphocyte transformation.

Transfer factor preparations from 57 different donors have been compared for effects on mitogen- and antigen-induced lymphocyte transformation. Nine of the preparations were mitogenic when added to cultured lymphocytes although the magnitude of this activity was relatively low. The majority of the preparations (48/57) did not affect PHA-induced lymphocyte transformation although augmentation (6 of 57) and suppression (3 of 57) was observed with some. In addition we observed that most of the preparations tested suppressed ConA stimulation and augmented the PWM response. When selected preparations were evaluated on antigen-responsive cells, there was a correlation between the magnitude of antigen responsiveness and the magnitude of TF augmentation of antigen-induced lymphocyte transformation (p less than 0.005). Cultures that were not responsive to antigen (KLH-negative or BUdR-treated) could not be stimulated by TF from immune donors and antigen. These data suggest that TF preparations contain either stimulatory or inhibitory components and that TF is not capable of activating naive lymphocytes to undergo transformation in response to antigen.

Antigens↗
PubMed1975

Cell-mediated immunity in experimental allergic encephalomyelitis: cross reactivity between myelin basic protein and mycobacteria antigens.

Guinea pigs injected with Freund's incomplete adjuvant emulsified with guinea pig spinal cord, purified guinea pig myelin basic protein, or human myelin basic protein showed dermal reactivity to both of the basic proteins as well as to mycobacteria antigens. Animals receiving only mycobacteria antigens expressed dermal reactivity to the sensitizing antigen in addition to basic protein. This cross reactivity may help explain the role of mycobacteria in inducing and protecting against EAE, and may have important implications concerning human demyelinating diseases.

Animals↗