Specific Antibody Activity Research Articles

Haemophilus influenzaelocalized in epithelial cell layers is shielded from antibiotics and antibody-mediated bactericidal activity

NonencapsulatedHaemophilus influenzaefrequently persists in the lungs of chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) patients for prolonged periods of time. The bacteria are not eradicated by antibiotic treatment of the patients or by specific antibodies that are found in the sputum and sera of these patients. We investigated whetherH. influenzae, when localized in lung epithelial cell layers, is shielded from antibiotics and from antibody-mediated bactericidal activity of specific antibodies. Anin vitromodel system consisting of lung epithelial NCI-H292 cells on permeable supports was developed to allow long term association ofH. influenzaewith the cells. Microscopic examination showed increasing numbers ofH. influenzaebacteria between the epithelial cells up to 24 h of incubation. Coinciding with the microscopic observations the maximum number of cell-associated bacteria surviving gentamicin treatment of the cell layers was obtained after 24 h of incubation. AllH. influenzaestrains, and oneHaemophilus parainfluenzaestrain tested penetrated into the cell layer as determined by gentamicin killing. Cell-associated bacteria were shielded from the bactericidal activity of several antibiotics and from antibody-mediated bactericidal activity. After prolonged incubation in the cell system in the presence of a specific bactericidal antibody against major outer membrane protein (MOMP) P2, antigenic variation occurred due to a point mutation in the MOMP P2 gene, similar to point mutations observedin vivo. We conclude that penetration ofH. influenzaebetween lung epithelial cells results in shielding the bacteria from killing by antibody dependent defense mechanisms and by antibiotics. Therefore, penetration ofH. influenzaebetween epithelial cells may contribute to the persistence of this microorganism in COPD and CF patients.

Antiparasite activity of sea-anemone cytolysins onGiardia duodenalis and specific targeting withanti-Giardia antibodies

The killing activity of sea-anemone cytolysins on Giardia duodenalis wasinvestigated. Three different toxins, sticholysin I and II from Stichodactyla helianthus (St I and St II) and equinatoxin II from Actinia equina (EqtII) were all found to beactive in an acute test, with a C 50 in the nanomolar range (St I, 0.5 nM; St II, 1.6 nM; and EqtII, 0.8 nM). A method to target the cytolysin activity more specifically towards theparasite cells by using anti- Giardia antibodies was then investigated. Parasite cells weresensitised with a primary murine monoclonal or polyclonal antibody followed by a biotinylatedsecondary anti-mouse-IgG monoclonal antibody. Subsequently, avidin and a biotinylated EqtIImutant were added, either in two separate steps or as a pre-formed conjugate. When themonoclonal antibody was used, the C 50 of biotinylated EqtII was 1.3 nM withsensitised cells and 5 nM with non-sensitised cells, indicating a four-fold enhancement of activitywith the cell treatment. Treatment with the polyclonal antibody was somehow more effective thanwith the monoclonal antibody in an acute test. This indicates that sea-anemone cytolysins canefficiently kill Giardia cells, and that it is possible to improve, to a certain extent, theanti-parasite specificity of these toxins with anti- Giardia antibodies. However, thefeasibility of this approach in vivo remains to be demonstrated. © 1999 Australian Society forParasitology

Functional and immunogenic characterization of two cloned regions of Streptococcus mutans glucosyltransferase I.

Glucosyltransferase (GTF) enzymes of mutans streptococci are considered virulence factors due to their ability to synthesize adhesive glucans, which facilitate cell-to-cell adherence and accumulation. In this study we report the cloning, expression, and characterization of the catalytic (CAT) and glucan-binding (GLU) domains of S. mutans GTF-I encoded by gtfB. The CAT and GLU polypeptides represent amino acid residues 253 to 628 and 1183 to 1473, respectively, of S. mutans GTF-I. Antibodies to recombinant CAT and GLU were generated in rabbits and purified by affinity chromatography. Purified anti-CAT antibodies significantly inhibited water-insoluble glucan synthesis by S. mutans and S. sobrinus GTFs (P < 0.0001 and P < 0.05, respectively). The purified anti-GLU antibodies significantly inhibited both water-insoluble and water-soluble glucan synthesis by S. mutans GTFs (P < 0.0001 and P < 0.05, respectively). These results demonstrate that anti-CAT and anti-GLU antibodies are capable of inhibiting a variety of GTF activities. Since antibodies to S. mutans in saliva are implicated in protection against disease, we next assessed the ability of CAT and GLU polypeptides to induce mucosal antibody responses in mice. Intranasal (i.n.) immunization of mice with CAT showed significantly (P < 0.005) elevated levels of specific immunoglobulin G (IgG) antibody activity in serum and specific IgA antibody activity in serum, saliva, vaginal washes, and fecal samples. GLU immunized animals showed significantly (P < 0.005) elevated levels of specific IgA antibody activity in serum and vaginal secretions. Taken together, these results demonstrate that the recombinant CAT and GLU polypeptides are effective in inducing both mucosal and systemic immune responses. The ability of these polypeptides to induce a mucosal IgA immune response in mice after i.n. immunization supports their use as subunit vaccine candidates in the development of an anticaries vaccine.

IgM levels and specific antibody activity of the flounder (Platichthys flesusL.), following injection of microsporidian spores

IgM levels and specific antibody activity of the flounder (Platichthys flesusL.), following injection of microsporidian spores

Immune responses against major outer membrane antigens of Neisseria meningitidis in vaccinees and controls who contracted meningococcal disease during the Norwegian serogroup B protection trial.

Sera from vaccinees and controls who contracted serogroup B meningococcal disease during the blinded and open parts of a two-dose protection trial in Norway were compared for antigen-specific and bactericidal antibodies against vaccine strain 44/76 (B:15:P1.7,16). From 16 of 20 (80%) vaccinees and 26 of 35 (74%) controls, one or more serum samples (n = 104) were collected during the acute phase (1 to 4 days), early convalescent phase (5 to 79 days), and late convalescent phase (8 to 31 months) after onset of disease. Binding of immunoglobulin G (IgG) to the major outer membrane antigens (80- and 70-kDa proteins, class 1, 3, and 5 proteins, and lipopolysaccharide [LPS]) on immunoblots was measured by digital image analysis. Specific IgG levels in vaccinees increased from acute to early convalescent phases, followed by a decline, while controls showed a small increase over time. Vaccinees had significantly higher levels than controls against class 1 and 3 porins and LPS in acute sera, against all antigens during early convalescence, and against class 1 and 3 porins in the later sera. Vaccinees who were infected with strains expressing subtype P1.7,16 proteins demonstrated a level of IgG binding to protein P1.7,16 with early-convalescent-phase sera that was fourfold higher than that of those infected with other strains. Bactericidal titers in serum against the vaccine strain were 192-fold higher for vaccinees than those for controls during early convalescence, but similarly low levels were found during late convalescence. A vaccine-induced anamnestic response of specific and functional antibody activities was thus shown, but the decrease in protection over time after vaccination indicated that two vaccine doses did not induce sufficient levels of long-term protective antibodies.

Immunoglobulin G, plasma cells, and lymphocytes in the murine vagina after vaginal or parenteral immunization with attenuated herpes simplex virus type 2.

This investigation evaluated immunity to vaginal herpes simplex virus type 2 (HSV-2) infection after local or parenteral immunization with attenuated HSV-2. Vaginal immunization induced sterilizing immunity against challenge with a high dose of wild-type virus, whereas parenteral immunizations protected against neurologic disease but did not entirely prevent infection of the vagina. Vaginal immunization caused 86- and 31-fold increases in the numbers of immunoglobulin G (IgG) plasma cells in the vagina at 6 weeks and 10 months after immunization, whereas parenteral immunizations did not increase plasma cell numbers in the vagina. Vaginal secretion/serum titer ratios and specific antibody activities in vaginal secretions and serum indicated that IgG viral antibody was produced in the vagina and released into vaginal secretions at 6 weeks and 10 months after vaginal immunization but not after parenteral immunizations. In contrast to the case for plasma cells, the numbers of T and B lymphocytes in the vagina were similar in vaginally and parenterally immunized mice. Also, lymphocyte numbers in the vagina were markedly but similarly increased by vaginal challenge with HSV-2 in both vaginally and parenterally immunized mice. Lymphocyte recruitment to the vagina after virus challenge appeared to involve memory lymphocytes, because it was not observed in nonimmunized mice. Thus, local vaginal immunization with attenuated HSV-2 increased the number of IgG plasma cells in the vagina and increased vaginal secretion/serum titer ratios to 3.0- to 4.7-fold higher than in parenterally immunized groups but caused little if any selective homing of T and B lymphocytes to the vagina.

Avidity and Bactericidal Activity of Specific IgG Antibody Elicited by Immunization Against Haemophilus influenzae type b (Hib) with a Combined DTaP-Hib-Hepatitis B Vaccine in Infants ♦ 929

We previously showed that a diphtheria and tetanus toxoids with acellular pertussis (DTaP) vaccine when combined with Haemophilus influenzae b(Hib) polysaccharide (PRP) conjugated to tetanus toxoid (PRP-T) vaccine and Hepatitis B (HB) vaccine as a single injection: (1) does not produce equivalent anti-PRP antibody levels to those achievable with separate injections in infants following a three dose primary sequence at 2, 4 and 6 months of age; but (2) vaccinees producing low or undetectable anti-PRP antibody responses achieve high-titered, IgG-predominant responses when given a booster of PRP-conjugate (CRM197-OS) vaccine 3-7 months later, suggestive of a memory response (Clin Infect Dis 1997;25:1378-1384). Here, we assessed the avidity and bactericidal activity (BA) of the sera from these infants to further characterize the immunologic responses and the functional capacity of the antibodies produced. Avidity of the anti-PRP antibody was quantitated by use of a chaotropic agent (2.5-6.0M urea) in an ELISA with results expressed as percent of antibody bound to PRP after chaotropic exposure. BA was measured by a standard in vitro assay with wild Hib (strain Eagan). CBER lot 1983 anti-PRP antisera was used as a reference for both assays. Avidity and BA of 39 sera (post primary DTaP-PRP-T-HB combined vaccine, pre-CRM197-OS boost and post-boost) from infants with anti-PRP antibody levels 1.0 μg/ml. In vaccinees with 1 μg/ml of IgG anti-PRP antibody the post primary value was 66% (61-71%) and for the CBER standard it was 59% (53-65%); 1 μg/ml group post primary (p<0.001). BA of the anti-PRP antibody was correlated with total anti-PRP IgG antibody (r=0.61, p<0.001). We conclude that despite low post priming anti-PRP antibody levels, the studied DTaP-PRP-T-HB combination vaccine (manufactured by SmithKline Beecham) elicits antibody of high avidity, affinity maturation as seen in memory responses appears to occur in the absence of further antigen exposure from post primary to pre-boost even in those with very low anti-PRP antibody, and the elicited anti-PRP antibody is bactericidal.

Intracoronary-stent placement for coronary artery disease

which she removed and kept. The tick was identified as Dermacentor marginatus, a species found across Europe. She was admitted to hospital on suspicion of having Lyme disease. She complained of a severe headache and on examination was found to have a necrotic eschar on the occiput surrounded by a reddish halo (figure) and four enlarged occipital lymph nodes. She received doxycycline and soon became afebrile, but she continued to complain of severe headaches, general weakness, and tiredness for 2 months. She seroconverted against R conorii and R slovaca by microimmunofluoresence but antibody levels remained low (titre 1:128). Western blot analysis showed specific antibody activity to R slovaca. No antibodies to Borrelia burgdorferi were found. R slovaca was isolated from the tick but not the blood and scalp sampled 48 h after treatment began. However, when a DNA extract prepared from the skin biopsy was incorporated into Rickettsia-specific PCR on amplification products obtained. The base sequence of this product (an RompA gene fragment) was found to be indistinguishable from that of R slovaca, strain 13-B. 3

Alterations in total protein, IgM and specific antibody activity of male and female sea bass (Dicentrarchus labraxL., 1758) sera following injection with killedVibrio anguillarum

The relationship between the levels of total proteins, immunoglobulins and antibody activity in serum of sea bass broodstock, following one or two intraperitoneal injections of heat-killedVibrio anguillarum(V1), was studied over a period of 10 months. Determination of immunoglobulin (IgM) level was carried out using a double monoclonal antibody sandwich ELISA and the specific antibody activity to V1 (AbV1) quantified by indirect ELISA. IgM level decreased during the first month post-immunisation (p.i.), but persisted at a high level from the third month until the eighth month p.i. in injected fish and until the tenth month p.i. in boosted fish. AbV1 level increased after 2 weeks and remained elevated for longer than 10 months p.i. Neither the IgM nor the AbV1 levels of control fish were changed following an injection of phosphate-buffered saline. The V1 injection did not modify the protein level, but alteration of protein levels over time differed between males and females. Moreover IgM production was significantly higher, but no significant difference was found between males and females in AbV1 production. The decrease of IgM level after injection may be explained by consumption of IgM, with paratopes close to the injected antigen epitope, which are mobilised to compensate for the lack of the specific antibodies. This early decrease is likely to be an adaptation rather than a deficiency of the immune system.

Immunoglobulin deficiencies and impaired immune response to polysaccharide antigens in adult patients with recurrent community-acquired pneumonia.

The frequency of humoral immunodeficiencies was analysed in 39 patients with a history of recurrent (> or = 3) episodes of community-acquired pneumonia. Total immunoglobulin levels and/or IgG subclass levels were low in 14 patients (36%), including eight patients with IgG or IgG2 deficiency. The specific antibody activity to pneumococcal capsular polysaccharides (serotypes 3, 6A, 19F, and 23F) and to phosphorylcholine was low in the IgG/IgG2-deficient patients compared to 36 healthy controls, and they also responded poorly to vaccination with a 23-valent pneumococcal capsular polysaccharide vaccine. The remaining 25 patients, with normal immunoglobulin and IgG subclass levels, had specific anti-pneumococcal antibody levels comparable to the healthy controls, and all but 3 responded to vaccination. We conclude that immunoglobulin deficiencies and the inability to respond to polysaccharide antigens are common risk factors for recurrent pneumonia in adult patients. Immunoglobulin levels (including IgG subclasses) and antibody response to polysaccharide antigens should be investigated in these patients.

Tolerance to appetite suppression induced by peptidoglycan.

Physiologically realistic peptidoglycan (PG) fragments, derived from Neisseria gonorrhoeae, were shown previously to dose-dependently suppress food consumption and body weight gain in rats following single intraperitoneal injections. The present study, examining the effects of repeated daily injection of PG, provides additional support to our underlying hypothesis, i.e., that soluble PG fragments contribute to the loss of appetite commonly associated with bacterial infections. An initial intraperitoneal injection of purified, soluble, macromolecular, extensively O-acetylated PG fragments (S-O-PG) (240 micrograms/kg of body weight) decreased overnight food consumption in male Lewis rats (150 g) by approximately 35% relative to animals receiving diluent alone (P < 0.05). However, subsequent daily injections of S-O-PG resulted in progressively smaller effects on food consumption until, by the fourth day, rats were completely nonresponsive (tolerant) to S-O-PG-induced hypophagia. Rats that developed tolerance to the effects of S-O-PG on appetite were also tolerant to three other known hypophagic agents, lipopolysaccharide (LPS), muramyl dipeptide, and interleukin-1, when challenged one day after establishment of S-O-PG tolerance. Similarly, rats developed tolerance to repeated injections of muramyl dipeptide or LPS and were cross-tolerant to S-O-PG when challenged 1 day later. However, 30 days after establishment of S-O-PG tolerance, rats remained nonresponsive to S-O-PG but regained full responsiveness to LPS-mediated hypophagia. Thus, at least two mechanisms of tolerance to S-O-PG hypophagia exist: an early tolerance which is nonspecific and a late tolerance which is specific for S-O-PG. Late, but not early, tolerance to S-O-PG-mediated suppression of appetite was associated with an increase in specific anti-PG antibody activity as measured in an enzyme-linked immunosorbent assay.

Decreased expression of mannose-specific adhesins by Escherichia coli in the colonic microflora of immunoglobulin A-deficient individuals

Most Escherichia coli isolates can express type 1 fimbriae with mannose-specific adhesins. These adhesins bind to the oligosaccharide chains of secretory immunoglobulin A (IgA). Thus, in addition to specific antibody activity, secretory IgA possesses a broad reactivity with bacteria expressing type 1 fimbriae. The absence of secretory IgA in colonic secretions, as seen in IgA deficiency, might therefore alter the ability of type 1-fimbriated E. coli to colonize the large intestines of these individuals. In the present study, 10 E. coli isolates from each of 17 IgA-deficient and 17 age-matched control individuals were assessed for the carriage of the fim gene cluster by DNA-DNA hybridization and for the expression of type 1 fimbriae by hemagglutination of guinea pig erythrocytes. The contribution of type 1-fimbria-mediated adherence to HT-29 colonic cells was also analyzed. The proportion of fim+ E. coli isolates was lower in IgA-deficient than in control individuals (74 versus 94%, P < 0.05), as was the proportion of isolates expressing type 1 fimbriae in vitro (69% versus 85%, P < 0.05). The median mannose-sensitive adherence to HT-29 cells was lower for isolates from IgA-deficient individuals than from the controls (9 versus 26 bacteria per cell, P < 0.05). Isolates expressing type 1 fimbriae showed lower adherence to HT-29 cells when they were derived from IgA-deficient individuals than when they were derived from control individuals (15 versus 27 bacteria per cell, P < 0.05). The results suggest that the interaction of type 1 fimbriae with secretory IgA contributes to the large intestinal colonization by these bacteria.

Cell surface protein disulfide-isomerase is involved in the shedding of human thyrotropin receptor ectodomain.

In human thyroid glands the TSH receptor undergoes a cleavage reaction which yields to an extracellular alpha subunit and a membrane spanning beta subunit linked together by disulfide bridges. A similar reaction is observed in transfected L cells although some uncleaved monomers persist in these cells. We have recently shown that the alpha subunit of the TSH receptor undergoes partial shedding in human thyroid cells and heterologous cells permanently transfected with an expression vector encoding the receptor. This shedding is a two-step process. The first step consists in the cleavage of the proreceptor at the cell surface probably by a matrix metalloprotease and the second step in the reduction of the disulfide bridge(s) (Couet, J., Sar, S., Jolivet, A., Vu Hai, M. T., Milgrom, E., & Misrahi, M. 1996, J. Biol. Chem. 271, 4545-4552). We have used the transfected L cells to study the second step involved in sTSHR shedding. The membrane impermeant sulfhydryl reagent DTNB (5,5'-dithiobis(2-nitrobenzoic acid) allowed us to confirm that the reduction of the TSH receptor disulfide bonds occurred at the cell surface. The antibiotic bacitracin even at low concentrations also elicited a marked inhibition of TSH receptor shedding. This led us to implicate the enzyme protein disulfide isomerase (PDI, EC 5.3.4.1) in this process. We thus tested the inhibitory activity of specific monoclonal antibodies raised against PDI. All antibodies elicited a marked inhibition of sTSHR shedding. This confirmed that cell surface PDI is involved in the shedding of the TSH receptor ectodomain. The shed alpha subunit may be at the origin of circulating TSH receptor ectodomain detected in human blood.

Detection of salivary and seric IgG and IgA antipooled pigeon sera activities in patients with pigeon breeder's disease

Pigeon breeder's disease (PBD) is an interstitial lung disease induced by exposure to pigeon antigens. Search of antipigeon antigen antibodies (APSA) in serum or bronchoalveolar lavage is generally used for auxiliary diagnostic purposes. However, APSA can be present in a number of exposed but asymptomatic individuals as well as in patients with other interstitial lung diseases who live in areas where keeping pigeons is a common domestic habit. In this study, saliva was evaluated as an alternative means to serum for APSA detection by ELISA using pooled pigeon sera as antigen. Serum and saliva samples obtained from 17 patients with PBD, 14 with idiopathic pulmonary fibrosis (IPF), 19 asymptomatic relatives (AR) exposed to pigeon antigens, and 27 clinical healthy voluntary subjects (CHVS) were tested for IgG and IgA APSA. Our results showed that both fluids obtained from PBD patients exhibited a significantly higher specific IgG antibody activity compared to the other groups. Serum optical density (O.D.) values for PBD were 1.187 +/- 0.738 vs. 0.024 +/- 0.033, 0.255 +/- 0.471, and 0.204 +/- 0.346 for CHVS, AR and IPF, respectively (P < 0.05). Salivary O.D. for PBD were 0.801 +/- 0.447 vs 0.010 +/- 0.011, 0.104 +/- 0.151, and 0.22 +/- 0.447 (P < 0.05). In contrast, serum specific IgA did not discriminate between PBD and IPF patients. In addition, although the PBD group exhibited the highest values of IgA salivary APSA, high levels were also observed in saliva specimens from CHVS, a group of normal individuals who deny pigeon exposure. These findings suggest that measurement of IgG salivary APSA can play a role in the evaluation process of patients with pigeon breeder's disease.

Antibody Response in Bronchoalveolar Lavage and Serum of Rats after Aerosol Immunization of the Airways with a Well-Adhering and a Poorly Adhering Strain of &lt;i&gt;Streptococcus pneumoniae&lt;/i&gt;

This study describes the antibody response to two bacterial antigens, pneumolysin toxoid (PL) and purified pneumococcal capsular polysaccharide (PPS) 19F, in bronchoalveolar lavage (BAL) and in serum in rats after aerosol immunization with whole killed Streptococcus pneumoniae. To study the importance of bacterial adherence for antibody formation, one well-adhering and one poorly adhering strain of S. pneumoniae was used. The results show local specific anti-PPS 19F IgA, IgM and IgG antibody activities after aerosol immunization. Anti-PL antibody activity in all three immunoglobulin classes was found, although the anti-PL activity was lower than the anti-PPS 19F antibody activity. The IgA anti-PPS 19F antibody activity in BAL after immunization with the well-adhering strain was higher than with the poorly adhering strain. We conclude that aerosol immunization with S. pneumoniae induces a local, specific antibody production in the lung of the rat.

Platelet activation by Streptococcus sanguis is mediated by specific antibody and alternative complement pathway activation via the Fc receptor

Platelet activation by Streptococcus sanguis is mediated by specific antibody and alternative complement pathway activation via the Fc receptor

Stability of bovine immunoglobulins to thermal treatment and processing

Thermal stability of bovine immunoglobulin (IgG) in model systems and in commercially processed milk products was investigated. Bovine serum IgG dissolved in either phosphate buffered saline (PBS), boiled milk or ultra high temperature (UHT) sterilized milk was heated at temperatures ranging from 62.7 °C to 80 °C. The D-values ranged from 90, 200 and 170 s at 80 °C to 25.5, 27.2 and 32.8 min at 72 °C for IgG in PBS, boiled milk and UHT milk, respectively. These results suggest slightly greater thermal stability of IgG in milk than in phosphate buffer. IgG content was not changed after 30 min at 62.7 °C, nor by holding for 24 h at either ambient temperature or 4 °C. Over the temperature range from 72 ° to 80 °C, z-values were 6.7, 8.9 and 8.5 °C, and energies of activation were 353.5, 258.2 and 298.5 kJ mol −1 for thermal destruction of bovine serum IgG in PBS, boiled milk and UHT milk, respectively. These findings in model systems suggest that commercial pasteurization processes should not result in complete destruction of IgG. Comparison of IgG content in raw milks and corresponding HTST-pasteurized milks of varying fat content indicated 59–76% retention after pasteurization, with no apparent effect by either homogenization, skimming or standardization to 1 or 2% fat levels. The IgG contents and specific antibody activity against lipopolysaccharide fractions of five bacteria were determined for several commercially processed milk products. HTST-pasteurized milks, reconstituted skim milk powder and whey from cheddar cheese production all showed high levels of IgG and specific antibody activity. However, canned evaporated milk and ultra high temperature (UHT) sterilized milk had little or no IgG. This study demonstrates the dependence of bovine IgG stability in milk products on severity of thermal treatment used in various commercial processes.

Immunoglobulin Concentration and Specific Antibody Activity in Oocytes and Eggs of Immunized Red Sea Bream

Immunoglobulin Concentration and Specific Antibody Activity in Oocytes and Eggs of Immunized Red Sea Bream

Induction of type I hypersensitivity in guinea pigs after inhalation of phthalic anhydride

Guinea pigs were exposed through inhalation to phthalic anhydride (PA) dust at 0.5, 1.0, and 5.0 mg/m3, 3 hours/day for 5 consecutive days. Inhalation challenge with aerosolized phthalic anhydride-guinea pig serum albumin (PA-GPSA) conjugate elicited immediate-onset respiratory reactions in animals exposed to all three levels of dust. Inhalation challenge of a subgroup of animals with phthalic anhydride dust did not elicit an immediate response, as measured by changes in respiratory frequency and plethysmograph pressure. Serologic studies showed that these animals had allergic IgG1a antibody to PA-GPSA. There was a dose-dependent increase in specific IgG antibody activity, as measured by ELISA. Animals exposed to and challenged with 5.0 mg/m3 PA dust had significant numbers of hemorrhagic lung foci. Those animals with the greatest number of foci had high IgG antibody activity to PA, as measured by ELISA. This study showed that exposure to levels of PA dust as low as 0.5 mg/m3, below the current threshold limit value of 6.0 mg/m3, can sensitize animals to produce allergic antibody.

Increased proliferative activity, loss of β-adrenergic receptor function and class I major histocompatibility complex antigen surface expression in a modified lymphoma cell line

The molecular interaction of class I major histocompatibility complex (MHC) antigens (Ag) and of beta-adrenergic receptors was previously demonstrated on lymphocytes. By long-term culturing with high concentration of foetal calf serum, the murine S49 lymphoma cell line was modified (S49m) giving phenotypic alterations in beta-adrenergic receptors and class I Ag expression. S49m cells displayed a reduced number of beta-adrenergic sites that were uncoupled to the adenylate cyclase system. These were unable to respond to beta agonist stimulation, despite the fact that direct activation of Gs could be achieved with aluminium tetrafluoride. Although S49m cells showed normal expression of the thy 1.2 Ag, they displayed no expression of class I Ag of the d haplotype. This was assessed by the evident lack of cytotoxic activity of specific monoclonal antibodies (Mo Ab) and of their binding. When performing IFI staining on permeabilized cells, we found positive staining with anti-class d Ab inside the cell. This loss of expression and activity of beta-adrenoceptors and the internalization of class I Ag were accompanied by a higher rate of proliferation in S49m cells. The possibility that the loss of both molecules would modify the biology of the cell is also discussed.