A 30-minute preparative method for isolation of IgG from human serum

Experimental design for vaccine preparations against human malignant tumors

The cancer cell is immunoresponsive and indirectly immunocompetent cell inserting itself in an extremely delicate system of natural antibodies and their respective anti-idiotypes. In regulatory sense it mimicks--in the Richter's model of immune system function--second order of response by antigenic cell surface product of malignant transformation, acting functionally as incomplete anti-idiotypic antibody (homobody) with exteriorized tumor antigen. It successfully competes with the natural anti-idiotypic antibodies replacing their repressive function by inducive one, and by doing so, changing natural antibody response by two orders of magnitude. The proposed experimental design would hybridize in separate experiments in one molecule: anti-HLA and anti-tumor xenogeneic antibodies obtained from animals and used for passive immunization; unaltered tumor antigen with organ-specific histocompatibility antigen having a preserved capacity of associative recognition. The latter process of humoral exteriorization of antigens would be elicited in animals and these immunoglobulin molecules (homobodies) would be used in humans for active immunization or in isogeneic animals for a production of antisera for passive immunization. Both these types of immunization would revert deranged immunological response in the cancer patient back to its normal order. Appropriate absorptions at critical steps would assure high specificity of the antisera.

Removal of hepatitis B virus infectivity from human gamma-globulin prepared by ion-exchange chromatography

Hepatitis B virus infectivity can be removed from human plasma used to prepare a gamma-globulin product by ion-exchange chromatography with commercially available resins. A pooled human plasma sample free of hepatitis markers was contaminated with 10,000 chimpanzee infectious doses of hepatitis B virus per milliliter from a known infectious inoculum. The contaminated plasma was diluted to yield a weakly positive radioimmunoassay result for HBsAg and then processed over a double-column chromatography system containing anionic ion-exchange resins to yield highly purified gamma-globulin. Two chimpanzees were each inoculated intravenously with this product while a control animal received non-treated material. The 2 experimental animals each received a potential challenge of 3,000 ID and showed no serologic evidence of the disease during 9 months of evaluation. The control animal received 100 ID and developed hepatitis B 25 weeks after the challenge.

A F(ab')2 fragment blocking study of the HLA-B14 antigen

The HLA-B14 antigen exists in two serologically distinct forms termed Bw64 and Bw65. These two B14 subgroups were studied using the ability of F(ab')2 fragments from HLA-B14 and Bw6 antisera to block the binding of cytotoxic HLA antibodies directed towards the same or an adjacent antigenic site. The findings suggest that the B14 antigen consists of several antigenic determinants some of which are spatially distinct and others which are closely associated. A "common" determinant possessed by both B14 subtypes is proposed which is separate from a Bw64 (or Bw65) site. Additional determinants that B14 shares with B8, B18 and B38/B39 appear to be distinct from the Bw64/Bw65 site, variably associated with the B14 "common" determinant but closely adjoining the Bw6 antigen.

Detection of antibody-coated sperm by 'panning' procedures

The use of 'panning' procedures to detect immunoglobulin on the sperm surface are described. Wells on plastic plates are coated with anti-immunoglobulin molecules by either 1-step or 2-step procedures and the sperm under test are then incubated in these wells for up to 1 h and the wells washed. Antibody-coated sperm remain attached in large numbers while control sperm are washed out. These procedures have the advantages that they are cheap, simple, do not involve sperm fixation and may be used with relatively dilute cell suspensions and with sperm of low motility. The potential applications of the procedures are discussed.

Human factor IX inhibitors: immunochemical characteristics and treatment with activated concentrate

Plasma was obtained from two patients with severe factor IX deficiency who had developed specific inhibitors of factor IX. Immunochemical characterization of the inhibitors by coagulation inhibitor neutralization assays and by immunoelectrophoretic methods demonstrated that both were IgG antibodies. One of the antibodies appeared to be monoclonal in origin with IgG subclass 4 heavy chains and lambda light chains. The other appeared to be oligoclonal and contained IgG subclass 1 and subclass 4 heavy chains and kappa and lambda light chains. One of the patients was treated with conventional, non-activated factor IX concentrate and with activated factor IX concentrate (Feiba) for repeated bleeding episodes. Administration of Feiba resulted in a progressive shortening of the kaolin cephalin clotting time and was followed by a good clinical response. Infusion of non-activated factor IX concentrate failed to induce clinical resolution of haemarthroses and had minimal effect on laboratory tests. The presence of circulating immune complexes could not be demonstrated in this patient.

Improved radioimmunodetection of tumours using liposome-entrapped antibody

The discrimination of radioimmunodetection of tumours is reduced by the presence of circulating radiolabelled antibody (primary antibody). We have prepared liposomes containing an antibody to the primary antibody (secondary antibody), with the intention of complexing and delivering to the liver primary antibody which is not associated with the tumour. In mice bearing xenografts of human tumours which secrete the marker carcinoembryonic antigen (CEA), liposomally entrapped secondary antibody was able to reduce the blood levels of 125I-labelled anti-CEA within 2 h, without reducing the amount of anti-CEA bound to the tumour. We therefore suggest that the use of liposomally entrapped secondary antibody would improve the diagnostic potential of radioimmunodetection of tumours and their metastases.

Partial purification of anti-DNA antibodies from systemic lupus erythematosus serum by dye-ligand chromatography

Purification of anti-DNA antibodies from systemic lupus erythematosus (SLE) serum is usually achieved by DNA-affinity chromatography. However, using DNA-cellulose, the present study has found that this technique results in very low yields of DNA binding activity, much of which is contaminated with DNA simultaneously released during chromatography. In comparison it has been found that the anionic dyes Cibracon blue F3GA and Procion red HE3B, bound to crosslinked agarose, give more than 80% recovery and purification of DNA binding activity from whole SLE serum of 11- and 7-fold respectively. The majority of serum immunoglobulin did not bind to the dyes, but that which did, including anti-DNA antibody, bound by ionic interaction. Dye-ligand chromatography is therefore suggested as a useful technique for high yield recovery of partially purified DNA binding activity which can be subjected to further purification procedures, such as preparative isoelectric focusing.

The kinetics of DNAse inhibition by specific antibodies

The inhibition of beef pancreatic deoxyribonuclease I activity with specific antibodies is studied using the hypochromic shift of DNA at 260 nm. The kinetics of this reaction reveals two reaction phases. The first phase, which ends within seconds, is reversible and follows second order kinetics. It leads quickly to the formation of big complexes. The second phase, which reaches completion within minutes before precipitation is detectable, is essentially irreversible and follows zero order kinetics. A model explaining these results is suggested.

Inhibition of responder cell activity in mixed leukocyte culture reactions. I. Evidence of cross-reactivity of B7-antibody with HLA-B8

In a previous report we described a human allo-antiserum which showed MHC restricted dual specific inhibition of mixed leukocyte culture (MLC) reactions (de Rooij et al. 1980). Responder cells were preincubated with the antiserum and washed. Inhibition of MLC reactions occurred if HLA-B8 positive responder cells and HLA-B7 or B40 positive stimulator cells were used. The mechanism of inhibition by this antiserum was investigated and described in this report. The results strongly suggested that the observed inhibition was due to HLA-B7 specific antibody molecules cross-reacting with HLA-B8 antigens. We decided on the following mechanism: HLA-B7 specific antibody molecules bind to HLA-B8 antigens on responder cells at 4 degrees C. Bound antibody molecules area readily released at 37 degrees C and the bind preferentially to HLA-B7 or -B40 positive stimulator cells. Stimulator cells are then lysed by antibody dependent cellular cytotoxicity (ADCC), resulting in impaired MLC reaction. This conclusion was derived from the following observations: 1. HLA-B7 positive cells could be lysed due to antibody molecules bound to B8 positive cells: a. Cells coated with antibody molecules lysed B7 or B40 positive target cells. b. Antibody molecules released from B8 positive cells lysed B7 or B40 positive target cells in ADCC. 2. The active antibody molecules were HLA-B7 specific: a. The inhibiting antibody molecules in the antiserum could be absorbed on and eluted from HLA-B7 positive platelets (de Rooij et al. 1980). b. Antibody molecules bound to and released from HLA-B8 positive cells carried the same B7 specific inhibiting and cytotoxic activity as the original antiserum. 3. The site of recognition on HLA-B8 positive cells is the HLA-B8 antigen: a. F(ab')2 preparations from HLA-B8 and -Bw6 specific antisera inhibited antibody binding to B8 positive cells. b. Antibody binding was not restricted to B, T, FcR+, FcR- or non adherent cell subpopulations. 4. The antibody molecules bind to B8 positive cells with the antigen binding site and not with the Fc part of the molecule: a. Antibody binding could be blocked partially with a F(ab')2 preparation from the original antiserum but not with a Fc preparation. b. The antigen binding site of antibody molecules bound to HLA-B8 positive cells was not freely available, since the MLC inhibiting activity of sensitised B8 positive cells could not be blocked by soluble HLA-B7 antigens. c. The antiserum was cytotoxic for HLA-B8 positive target cells in ADCC. The observed inhibition of MLC by antibody molecules with apparent dual specificity is thus the consequence of a shared or a similar antigenic determinant of HLA-B7 and HLA-B8 antigen molecules.

Separation of immunoglobulin M (IgM) essentially free of IgG from serum for use in systems requiring assay of IgM-type antibodies without interference from rheumatoid factor

The proposed method was designed to replace the tedious and difficult separation of immunoglobulin M (IgM) from IgG by sucrose gradient sedimentation. In this method, a 250-microliter portion of serum diluted 20-fold was passed through a small column of quaternary aminoethyl-Sephadex A-50 ion exchanger. IgG was not retained, but additional washes were required to remove all but 5%. A second buffer-eluting fluid recovered an average of 80% of the original IgM in a defined dilution. The entire operation took 15 min. The efficiency of this process was evaluated by the following: (i) radial immunodiffusion measurements of IgG and IgM; (ii) recovery studies of isohemagglutinins; and (iii) demonstrated removal of interference by the rheumatoid factor. The method was applied successfully to distinguish rubella IgM antibody.

Semen-elicited accumulation of antibodies and leucocytes in the rabbit female tract

A marked increase in vascular permeability to proteins, including IgG, was observed in the reproductive tract of both virgin and parous rabbit does following insemination, leading to accumulation of immunoglobulins in the tissues and fluids of the reproductive tract.

The first example of an HLA-Bw45 antiserum produced in a HLA-Bw44 positive woman

An HLA-Bw45 serum (Mu46), which was produced by pregnancy in a Bw44 positive woman, is described. The serum was unable to be absorbed by Bw44 positive cells. Blocking tests employing broad B12 (Bw44 + Bw45) antisera, stimulated by either Bw44 or Bw45, showed that only F(ab)'2 from Bw45-stimulated B12 sera would completely block the cytotoxicity of this serum. It was concluded that Bw44 and Bw45 are distinct specificities which share common determinants. These findings are briefly discussed in relation to a recent report on the HLA-B antigen and supertypic Bw4, Bw6 antigen relationship.

Complement fixing activities of normal mammalian sera for homologous and heterologous sperm

The species of the natural anti-sperm antibodies found in normal mammals have been assessed using complement fixation tests. Heated rabbit sera showed complement fixing activity with both rabbit and guinea pig sperm, indicating that rabbit natural anti-sperm antibodies do not show clear cut species specificity in these interactions. On average, rabbit sera reacted more strongly with rabbit sperm that with guinea pig sperm but the difference fell short of statistical significance (P < 0.05) and there was considerable variation between sera in their anti-sperm activities. There were, however, clear species differences between rabbit and guinea pig sera in that heated guinea pig sera showed significantly weaker anti-sperm activity than heated rabbit sera (P < 0.005). Mouse vas sperm showed greater complement fixing activities (in combination with mouse serum) than did epididymal sperm (P = 0.05). These results are discussed in relation to possible functions of natural anti-sperm antibodies.

ADCC (K-cell)lysis of human erythrocytes sensitized with rhesus alloantibodies. I. Investigation of in vitro culture variables

An ADCC system has been developed using anti-D and papainized group O rhesus (D) positive red cells as the targets. Monocyte depleted mononuclear cell suspensions were effective in lysing appropriately sensitized red cells and papainization considerably enhanced the degree of specific lysis. Variation in culture volume and incubation in tubes or microplates were not critical to the degree of specific lysis obtained provided that the number of effector cells and target cells per culture was constant and the anti-D not diluted below the optimal concentration. Cytolytic activity was seen down to levels of 3 ng anti-D per culture. Specificity for lysis resided with the anti-D and not the effector cells. Several sources of anti-D were effective in inducing lysis of D positive red cells although individual variation was noted. Anti-c and anti-E were also shown to be effective in inducing specific lysis of red cells with the appropriate antigens.

ADCC (K-cell) lysis of human erythrocytes sensitized with rhesus alloantibodies. II. Investigation into the mechanism of lysis

The mechanism of lysis of anti-D coated human erythrocytes by human mononuclear K-cells was investigated. Red cell lysis was measurable after 30 min incubation and reached a maximum by 18--20 h. Cell-to-cell contact was necessary for lysis, phagocytosis was not a prerequisite, and intact microfilament function was required. The divalent cations Ca2+ and Mg2+ were both required for lysis to occur. Studies with metabolic inhibitors indicate that some RNA and protein synthesis is required for maximum expression of ADCC and intact microtubule function is essential. In the present system lysis was mediated by IgG1 anti-D antibodies and was significantly inhibited by IgG1 and IgG3 subclasses with some inhibition by IgG2 but not by IgG4, IgA or IgM. This suggests that the K-cell receptor is specific for IgG but that there is major cross-reactivity between IgG1 and IgG3. The inhibiting effect of hydrocortisone suggests that ADCC inhibition may be one mode of action of corticosteroids in ameliorating autoimmune haemolytic anaemia.

Spermotoxic properties of IgG fractions from normal rabbit sera

The antisperm activities of IgG fractions prepared from normal rabbit sera by three different techniques (ammonium sulphate precipitation, gel filtration, and DEAE-Sephadex absorption) were tested using a cytotoxic assay, and antisperm activity detected in fractions prepared by each of these techniques. The nature of the interactions between sperm and IgG molecules from normal sera, and possible functions of "natural" antisperm antibodies, are discussed.

On the problems of efficacy of separation of IgM and IgG by different methods

Using ultracentrifugation, gel filtration, and ion exchange, an attempt was made to completely separate immunoglobulin IgM and IgG present in pooled human serum of blood group O. The quality of separation was studied by testing IgG fractions for the presence of IgM by a sensitive detection method. It is demonstrated by rheophoresis that small amounts of IgM always remain detectable in the IgG fraction. This is of clinical importance because conclusions on the presence of specific antibody of different Ig classes are usually drawn under the assumption of complete separation. The control of the efficacy of the separation process using a sensitive detection method for Ig of different classes is recommended.

Evaluation of dithiothreitol (DTT) for inactivation of IgM antibodies

A newly introduced sulphydryl compound, dithiothreitol (DTT), is evaluated for its optimal conditions of inactivation of IgM antibodies. The maximal effects of DTT reagent are observed when its final concentrations are between 0.0025 M and 0.005 M, pH between 7.0 and 8.0, and incubation at 37 degrees C. Concentrations over 0.01 M, pH values greater than 8.0, and an incubation temperature over 40 degrees C resulted in a gel formation of the specimen. Examination of both 'cold' and 'warm' type antibodies demonstrated that the results obtained by the DTT reagent are in close agreement with those obtained by 2-mercaptoethanol reagents and DEAE Sephadex treatment. Since the procedure is simple and rapid and lacks offensive odour, DTT is recommended for routine use in blood banking for the inactivation of IgM antibodies.

Autoimmune antibodies in chronic lymphatic leukaemia

In chronic lymphocytic leukaemia a factor in patients' serum enhances the in vitro viability of the abnormal cells and this has been identified as an antibody. The activity of this factor can be removed by interaction with anti-immunoglobulin and by ammonium sulphate precipitation with a degree of saturation in excess of 46%. Cohn fractionation and chromatography with A-50 Sephadex show that the factor is not a complex but an immunoglobulin. No activity is removed after reaction of sera with 2-mercapto-ethanol and di-thiothreitol. The evidence therefore suggests that a gamma-G immunoglobulin is involved. Concentrated washings from the leukaemic cells behave in exactly the same way as patients' sera and activity is retained in the same fraction during precipitation and purification procedure. The extensive cross-reactivity of the sera suggests a common chronic lymphatic leukaemic antibody and it is considered that an active autoimmune response may be an integral part of the disease.

Immunochemical studies of infectious mononucleosis. VII. Isolation and partial characterization of a glycopeptide from bovine erythrocytes

The major sialoglycopeptide released from bovine erythrocytes by papain has been purified and characterized. The glycopeptide contains 82% by weight carbohydrate in molar ratios of galactose - 5.5:N-acetylglucosamine - 3.6:sialic acid - 2.6:N-acetylgalactosamine - 1.0. The carbohydrate and amino acid composition is quite different from the glycoprotein extracted from bovine erythrocyte stroma with hot 75% ethanol. The glycopeptide is devoid of reactivity with Paul-Bunnell heterophile antibody of infectious mononucleosis - an activity expressed to high degree on the bovine erythrocyte and associated with glycoprotein. The glycopeptide does react, however, with another antibody found in infectious mononucleosis as well as most normal human sera tested.

Autoimmune haemolytic anaemia with the unusual combination of both IgM and IgG autoantibodies

Two patients with autoimmune haemolytic anaemia of no obvious aetiology are presented. Both cases had IgM autoantibodies which were cold agglutinins with anti-I specificity and were complement binding. Both cases also had IgG autoantibodies which were incomplete, of wide thermal range and also had anti-I specificity, but were not complement binding. The red cells of both patients were coated with C4/C3d and IgG.

Inherited sialoglycoprotein deficiencies in human erythrocytes of type En[a-]

We have investigated the membranes of erythrocytes from a family in which there is a genetic defect [previously described as the En[a-] condition[ resulting in the loss of the major erythrocyte sialoglycoprotein [PAS-i]. The results show that two different types of sialoglycoprotein deficiency can be distinguished within this family. We suggest that the En[a-] group of variants is more appropriately described as a class of sialoglycoprotein deficient erythrocytes. Using a new technique it is shown that the blood group M antigen of normal erythrocytes is found only on the erythrocyte sialoglycoprotein while in this family the M antigen is found on membrane components other than the sialoglycoprotein. Our results suggest that the amino acid sequence of the sialoglycoprotein is important in defining the difference between the blood group M and N antigens in normal erythrocytes.

The use of the IgG fraction of typing sera in the lymphocytotoxic test: a comparison with other cytotoxic methods

The application of a simple batch method for the isolation of IgG from weakly lymphocytotoxic sera is described. The use of purified IgG as an antibody source at the serum concentration or up to tentimes that level resulted in the conversion of 25 out of 28 previously weak or non-reactive cytotoxic sera into potentially useful tissue typing reagents. The sensitivity of this technique was assessed by comparison with five cytotoxic test systems.

Serum antibody levels against T mycoplasmas in two North American Indian populations predisposed to spondylitis

Serum antibody levels against T mycoplasmas (Ureaplasma urealyticum) were determined by the metabolic inhibition method in several populations. A higher prevalence of antibody was found in Haida Indians and Bella Coola Indians than in blood donors, patients with rheumatoid arthritis, and patients attending a VD clinic. Antibody levels did not correlate with the presence of spodylitis or the histocompatibility antigen HLA-B27, although both these Indian populations have a high prevalence of spondylitis and HLA-B27.

Characterization of three new apparently related high frequency antigens

Three high frequency reactive antisera (Kir, Oca, Mil) are described which, based on serologic and genetic characteristics, identify a set of apparently related antigens. The antibodies react only by indirect antiglobulin technique against both adult and cord red blood cells, are primarily IgG, are not complement dependent nor enhanced by papain pretreatment of red blood cells, are high titered but of low avidity, and are not neutralized by serum nor absorbed by platelets. The antisera are not identical with, but may be related to, the Kna antibody. Population data show reactivity frequencies of 99.8 per cent for Kir, 98.7 per cent for Oca, and 96.4 per cent for Mil. The four phenotypes found are Kir+, Oca+, Mil+; Kir+, Oca+, Mil- Kir+, Oca-, Mil+ and Kir-, Oca-, Mil-. The occurrence of five unrelated triple negative individuals is greater than would be expected by chance alone for three independent antigens. Family studies demonstrate that the triple negative phenotype appears to be a recessive trait not linked to the Fy or MNS loci, and the Mil-trait is not linked to ABO, Jk, or HLA. Clinical observations following infusion of incompatible blood and in vivo survival studies of 51Cr tagged red blood cells indicate that the antigens, though potent immunogens, are not clinically significant.

Lymphoid cell dependent (K-cell) lysis of human erythrocytes sensitized with Rhesus alloantibodies

An in vitro homologous system using human Rhesus alloantibodies and target erythrocytes labelled with 51Cr has been used to demonstrate the ability of normal peripheral blood lymphoid cells to lyse antibody-coated human red cells. The results obtained suggest that this type of mechanism may be relevant to certain haemolytic diseases in man.

Optimal conditions for the use of sulphydryl compounds in dissociating red cell antibodies

Optimal conditions for the use of 2-mercaptoethanol (2-ME) and dithiothreitol (DTT) in the inactivation of IgM red cell antibodies were investigated. 0.2 M 2-ME was better than 0.01 M DTT; higher concentrations of these 2 substances could not conveniently be used because of gel formation. Incubation at 37 degrees C led to far more rapid inactivation than incubation at 22 degrees C; with 2-ME a period of 15 min at 37 degrees C was sufficient except with very potent antibodies, which were not inactivated even after 3 h incubation. When indirect antiglobulin tests were carried out on 2-ME-treated serum which had not been dialysed, false-positive results were obtained, although only with the mixture of equal volumes of undiluted serum and of 2-ME; results were negative in tests on dilutions of the mixture in saline. False-positive results could also be avoided by incubating the serum for 3 h with iodoacetamide, but this method also involves dilution of the serum. The only method whereby 2-ME-treated serum can be tested without diluting it and without obtaining false-positive reactions is to dialyse it overnight against saline. Since this method also gets rid of the noxious smell of 2-ME it is to be preferred for most purposes.

A simple method for the prediction of ABO incompatibility using Sephadex A-50. Prediction of ABO incompatibility

A rapid and simple method of demonstrating the presence of high titre IgG anti-A or anti-B (anti A/B) is described. The method requires the separation of IgG anti-A/B from IgM anti-A/B using DEAE Sephadex A-50 by a simple spin technique, and the subsequent titration of the IgG fraction to detect the presence of high titre IgG anti-A/B. Since high titre IgG anti-A/B is usually associated with ABO incompatibility the test is a useful guide to the prediction of ABO incompatibility in routine antenatal samples.

Persistence of rubellavirus-specific immunoglobulin M and immunoglobulin A antibodies: investigation of successive serum samples with lowered immunoglobulin G concentration

The persistence of rubellavirus-specific immunoglobulin (Ig) M and IgA antibodies has been studied in seven patients with primary postnatal rubella infections. Successive blood samples obtained over a period of several years after the onset of disease have been investigated, employing the fluorescent antibody technique and the sucrose gradient centrifugation method. IgM antibodies were found to persist for 4 to 5 weeks after the onset of disease, with only moderate variation being observed with respect to the different patients and the method of investigation being studied. The persistence of IgA antibodies (as examined by the fluorescent antibody technique) varied from a few weeks to several years after the onset of the disease. The detection of IgA antibodies cannot be considered as conclusive for the diagnosis of recent rubella infections.

The transmission of -125-I-labelled immunoglobulin G by proximal and distal regions of the small intestine of 16-day-old rats

1. Standard doses of -125-I-labelled rat IgG were injected into the intestinal lumen of rats aged 16 days, and their sera were sampled 2 and 3 hr later. High concentration quotients were obtained after injection into the proximal small intestime, whereas very little immunoglobulin was transmitted from doses injected into the terminal 20 cm of the small intestine. 2. The villi of the terminal 18--20 cm of the small intestine of 16-day-old rats, the region from which very little transmission of IgG occurred, were lined by tall columnar absorptive cells with very larg supra-nuclear vacuoles. The extent of the terminal intestine, in which this cell type predominated in the absorptive epithelium, varied with age. The importance of defining the precise location of the region of the intestine under examination is stressed. 3. The experimental results and the histological observations are discussed in relation to (a) the results which have been obtained using PVP, which is unsuitable as an indicator of immunoglobulin transport in the rat and (b) the histological composition of the absorptive epithelium and the maturation changes which affect the epithelium between 18 and 21 days.

The absorption of 125I-labelled immunoglobulin G by different regions of the gut in young rats

1. (125)I-labelled homologous IgG was injected into different regions of the small intestine of rats aged 12, 16, 18, 20 and 22 days. At 12 days the proximal and middle regions of the intestine readily absorbed globulin and transmitted it to the circulation. The distal region of the intestine transmitted little to the circulation at all ages tested.2. The intestine loses its ability to transmit globulin to the circulation in a distal-proximal direction. At 16 and 18 days the ability of the middle region had declined significantly, and this decline continued so that little globulin was transmitted from this region at 20 and 22 days.3. The proximal intestine retained the ability to transmit globulin to the circulation in significant amounts up to 20 days.4. There is a close negative correlation between body weight and total radioactivity of the sera of rats which had received doses of labelled globulin into the proximal and middle regions of the intestine. There was no such correlation after injection into the distal intestine - suggesting a restricted throughput of radioactive material by the absorptive cells of this region.5. These results are discussed in the context of the termination of antibody absorption, and in relation to the results obtained using polyvinyl pyrrolidone.