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P Liacopoulos

Publications and source records attributed to P Liacopoulos.

At least 55 records · Page 3Linked to original sources
PubMed1975

The potentiality of antibody-producing cells. I Bispecific cell occurrence in double stimulated cultures of syngeneic or allogeneic spleen cells of the mouse.

Cultures of spleen cells from Swiss, C57Bl or DBA/2 mice stimulated with 2,4,6-trinitrophenyl (TNP) conjugated sheep erythrocytes (SRBC) were used for studying the in vitro responses to TNP and native SRBC antigens and the frequency of occurrence of cells responding to both antigens. The response was revealed by plating the cultured cells with both native SRBC and TNP-conjugated pigeon erythrocytes (TNP--PRBC). Specific responses were obtained in all the cultures. Bispecific haemolytic plaque-forming cells (PFC) were detected in almost all cultures of individual Swiss mice cells with a frequency of 2-5--14 PFC/10(6) cells recovered. In DBA/2 cell cultures bispecific PFC were found in half the cultures (2-5--8-3/10(6) cells) and in C57Bl cell cultures in 30 per cent of the cultures (7--21/10(6) cells). When cells from individual Swiss mice immunized in vivo with TNP--SRBC were as an allogeneic culture from the 2nd day after immunization in the presence of TNP--SRBC, the frequency of bispecific PFC increased from 8 to 30/10(6) cells. Mixed allogeneic cultures of normal C57Bl and DBA/2 cells yielded high specific responses with regular occurrence of bispecific PFC only when the numbers of cells cultured together was small. However, when allogeneic cells were mixed 24 hours after starting the cultures, all responses were stimulated and bispecific PFC were found in considerable numbers (4--33/10(6) cells). Cross-reactivity between TNP--PRBC and native SRBC antigens was studied by culturing cells with each of the antigens and plating the cells with both, or by immunizing in vivo with SRBC or PRBC and culturing the cells with both antigens from the 2nd to the 5th day after immunization with both antigens. In no instance did bispecific PFC exceed background levels (0-1--0-6/10(6) cells) in these control experiments.

Animals↗
PubMed1975

Statistical study on double paraproteinemias. Evidence for a common cellular origin of both myeloma globulins.

Double paraproteinemias (DPP) are usually considered as resulting from a proliferation of two independent clones of cells. The present study describes a statistical analysis based on 141 published cases of DPP. The incidence of the heavy chain classes as well as of light chain types association has been compared with the frequency of occurence of the same H and L chains in simple paraproteinemias. Computation of the frequency of associations showed that different heavy chains are randomly associated in DPP. However, light chains are more frequently of the same type in both immunoglobulins more so than could be expected on the basis of a biclonal hypothesis (p less than 0.005). This preferential occurence of identical light chains suggests a linkage in the synthesis of two proteins and it favours a monoclonal origin of myeloma cells in DPP.

Humans↗
PubMed1975

Properties of bispecific rosette-forming cells. I.--Presence of T-lymphocyte markers.

Three T-cell markers have been used to determine the origin of bispecific rosette forming cells (RFC) observed after stimulation by two species of heterologous red cells. The inhibition by anti-theta serum (AOS), azathioprine (AZ) and anti-lymphocyte serum (ALS) of the majority of bispecific RFC indicates their T-cell origin. The study of their sensitivity to these inhibitors suggested that about half of the bispecific RFC belong to immature T1 cell subset and the other half to more mature T2 cells. Conversely, monospecific RFC include both B-celle RFC have characteristics different from monospecific RFC argues against the reaction of double RFC against a common antigenic determinant of the two erythrocyte types.

Animals↗
PubMed1975

Properties of bispecific rosette-forming cells. II. --Rosette formation by "educated" T-lymphocytes.

Normal thymus cells transferred into thymectomized and lethally irradiated syngeneic mice responded to stimulation with sheep erythrocytes by rosette formation with these erythrocytes. This response reached a peak on the 7th day and was not associated with any production of circulating antibodies. Rosettes produced by "educated" T-cells were inhibited by anti-theta serum as well as by anti-mouse Fab serum. Simultaneous stimulation of transferred thymocytes with sheep and pigeon erythrocytes provoked the appearance of a minority of cells simultaneously binding both types of erythrocytes. Depletion of B cells contaminating normal thymocyte populatins after passage through anti-mouse Ig coated columns before their transfer in thymectomized and irradiated recipients did not prevent the appearance of simple and double RFC. Moreover, when normal thymocytes or T-cells "educated" by allogeneic stimulation were incubated at 4 degrees C with anti-SRBC and anti-PRBC mouse sera a subsequent incubation at 37 degress of resulted in the dissociation of most passive rosettes formed at 4 degrees. Conversely similar incubation at 37 degrees of rosettes formed by actively immunized cells resulted in capping of about 50% simple and double rosettes. This redistribution of membrane receptors is proposed as a routine test for distinguishing active from passive rosettes.

Animals↗
PubMed1975

The potentiality of antibody-producing cells. II. Evidence for two antibody molecules of different specificities secreted by micromanipulated bispecific mouse spleen cells.

Bispecific PFC appearing on the 4th day after immunization of mice with sheep erythrocytes conjugated with trinitrophenyl hapten (TNP-SRBC) were identified by their capacity to lyse native SRBC and TNP-conjugated horse erythrocytes (TNP--HoRBC) simultaneously in an open carboxymethylcellulose medium. Individual PFC thus detected, were micromanipulated into two successive media containing the indicators SRBC and TNP--HoRBC. Out of 103 transferred double cells ninety-two (89 per cent) remained double in the second medium and of the ninety-two transferred into the third medium, fifty-four (58 per cent) provoked a double lysis, eighteen (19 per cent) provoked a single lysis and twenty (23 per cent) ceased to lyse. On the other hand, when the second medium contained the indicators and the soluble specific inhibitor (TNP--BSA), out of 156 transferred double PFC, 125 (80 per cent) became single and only nineteen (12 per cent) remained double. Of these cells, 136 were transferred into the third medium (not containing inhibitor) and here again sixty-five (48 per cent) became double, forty-nine (36 per cent) remained single and twenty-two (17 per cent) ceased to provoke any lysis. Other double PFC were micromanipulated from the original revealing medium into two successive media containing only one indicator and the homologous (second medium) or the heterologous third medium) soluble inhibitor (TNP--BSA or soluble SRBC antigen), in order to see whether a soluble inhibitor suppresses only the corresponding specific lysis. Out of 186 double PFC transferred into the media containing the indicator and the corresponding inhibitor 147 (79 per cent) were specifically inhibited, whereas out of 176 double PFC transferred into the third medium (in which about 20 per cent of the cells cease to function) containing one indicator and the unrelated inhibitor, 117 (66-6 per cent) lysed the indicator in spite of the presence of the unrelated inhibitor. Since a specific inhibitor suppresses the lysis of the corresponding indicator, whereas its presence does not interfere with the lysis of the unrelated indicator in the majority of double PFC, it can be concluded that these cells secrete two types of antibody molecules possessing different specificities.

Animals↗