Adult Red Blood Cells Research Articles

Monoclonal antibodies against adult and fetal red blood cells

Monoclonal antibodies against adult and fetal red blood cells

Blood group antigens on fetal red cells obtained by umbilical vein puncture under ultrasound guidance: a rapid hemagglutination test to check for contamination with maternal blood.

Seventy-two fetal blood samples obtained by umbilical vein puncture under ultrasound guidance for prenatal diagnosis and monitoring purposes were tested for the expression of 38 blood group antigens. The gestational age at sampling ranged from 18 to 34 wk with 76% of fetuses between 20 and 25 wk. Compared to adult red blood cells, the following antigens showed either abnormally decreased frequency, or significantly reduced expression: A, B, A1, H, Lua, Lub, Lea, Leb, P1, P, and I. Selected anti-I and anti-i cold agglutinins, active at room temperature, were used at appropriate dilution, in a rapid slide or spin test to check for possible mixture of the sample with maternal blood and were shown to detect contaminations up to 5%. The test has proved particularly helpful for immediate and in process assessment of foetal origin of the sampled blood.

Factors controlling the size of DNA loops in frog embryos and Friend erythroleukemia cells

Measurements were made of the average size of fluorescent halos of nucleoids of developing frog embryos, mouse fibroblasts (A9 cells) and Friend erythroleukemia cells cultured with various compounds. These halos are thought to represent relaxed lengths of loops of DNA attached to the nuclear matrix. Measurement of transcription of RNA from nuclei in vitro suggested that cells with more loops (smaller halos) had more initiation sites for transcription. DNA loop number decreases during development of the frog embryos, and red blood cells of adults have even fewer and larger loops. One or two days of culture of Friend cells in various compounds that induce differentiation resulted in more DNA loops than for control cells, but after 5 days of culture the differentiated erythrocytes had fewer DNA loops than control cells at stationary phase. Stationary phase cells have almost twice as many DNA loops as log phase cells. Various compounds that stall cells at the G1/S border induced more DNA loops, but subsequently the number of DNA loops decreased as the cells entered S phase. A number of compounds which slow the rate of cell division cause the formation of more DNA loops, perhaps due to longer G1 periods.

Role of O2-hemoglobin affinity in the regulation of cerebral blood flow in fetal sheep

Cerebral blood flow (CBF) and cerebral O2 transport (CBF X arterial O2 content) in the fetal sheep are nearly twice that in the adult, despite similar rates of cerebral O2 utilization. We tested the hypothesis that the difference depends on the increased oxyhemoglobin affinity in the fetus, using P50 (PO2 at which hemoglobin is 50% saturated) as the index of oxyhemoglobin affinity. We studied 18 unanesthetized fetal sheep in utero. In six animals the P50 was raised from 16.6 +/- 1.2 (SD) mmHg to 31.7 +/- 4.7 mmHg by exchange transfusing the fetus with adult sheep red blood cells. We measured CBF (with radioactive microspheres) and the PO2, PCO2, pH, and O2 content in carotid artery and sagittal sinus blood twice at the original P50 and twice after exchange transfusion. Arterial O2 content fell significantly at the higher P50. Since the fall in O2 content was not accompanied by a corresponding rise in CBF, O2 transport fell by 45%. Cerebral O2 consumption (CMRO2) did not change and cannot be implicated in the fall of O2 transport. E (the ratio CMRO2/O2 transport) rose by 77%. Sham exchange transfusions in six fetuses showed that the exchange transfusion procedure itself was not responsible for this alteration. To determine whether the fall in O2 transport and the rise in E was reproducible over a range of arterial O2 contents, a third group of six fetuses was studied. Fetal arterial O2 content varied from 4 to 12 vol%, first at P50 = 17 +/- 1.8 mmHg and again after exchange transfusion at P50 = 29.6 +/- 3.9 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Deformability and intrinsic material properties of neonatal red blood cells

Whole cell and membrane deformability are essential for red blood cell (RBC) survival and for effective blood flow. Neonatal RBCs display several specific properties (eg, large size, high hemoglobin F) that could influence their deformation characteristics and contribute to their shortened life span. The present study was designed to compare selected rheologic properties (cellular deformability, pressure required to aspirate RBC into micropipettes, static and dynamic viscoelastic material properties) of neonatal and adult RBCs. RBC deformability, as studied by a rheoscope, was similar for neonates and adults over a shear stress range of 2.5 to 500 dyn/cm2. The pressure required to aspirate RBCs completely into 3.3-micron diameter pipettes was 129 +/- 87 dyn/cm2 for neonatal RBCs and 71 +/- 37 dyn/cm2 for adult RBCs. The aspiration pressure for neonatal and adult RBCs increased with increasing RBC volume, suggesting that the increased mean aspiration pressure for neonatal RBCs resulted from their larger volume. When RBCs with same volume and diameter were compared, the aspiration pressure tended to be smaller for neonatal RBCs than for adult cells. To characterize material properties determining RBC deformability, we measured membrane extensional (shear) and bending elastic moduli, the time constant for elastic recovery from extensional deformation and hemoglobin viscosity (ie, cytoplasmic viscosity) of neonatal and adult RBCs. Membrane surface viscosity and time constant for recovery from bending deformation were calculated. The extensional and bending moduli of neonatal RBCs were slightly smaller (10% and 16%, respectively) compared with adult cells. This suggests that the static resistance of neonatal RBC membrane to deformation and failure in response to a given force is slightly smaller. The time constant for recovery from extensional deformation of neonatal RBCs was larger by 14%, compared with adult cells. The time constant for bending deformation related to the RBC diameter and surface area was increased by 18% in the neonates. Membrane surface viscosity and hemoglobin viscosity were similar for both cell types. These results indicate that the deformability and viscoelastic properties of neonatal RBCs deviate only slightly from those of adult RBCs and that the increased aspiration pressure of neonatal RBCs is solely due to their large size. Some of the specific deformation characteristics observed in this study (increased aspiration pressure, decreased resistance to elastic deformation) may contribute to the shortened life span of neonatal RBCs.

Deformability and Intrinsic Material Properties of Neonatal Red Blood Cells

Abstract Whole cell and membrane deformability are essential for red blood cell (RBC) survival and for effective blood flow. Neonatal RBCs display several specific properties (eg, large size, high hemoglobin F) that could influence their deformation characteristics and contribute to their shortened life span. The present study was designed to compare selected rheologic properties (cellular deformability, pressure required to aspirate RBC into micropipettes, static and dynamic viscoelastic material properties) of neonatal and adult RBCs. RBC deformability, as studied by a rheoscope, was similar for neonates and adults over a shear stress range of 2.5 to 500 dyn/cm2. The pressure required to aspirate RBCs completely into 3.3-micron diameter pipettes was 129 +/- 87 dyn/cm2 for neonatal RBCs and 71 +/- 37 dyn/cm2 for adult RBCs. The aspiration pressure for neonatal and adult RBCs increased with increasing RBC volume, suggesting that the increased mean aspiration pressure for neonatal RBCs resulted from their larger volume. When RBCs with same volume and diameter were compared, the aspiration pressure tended to be smaller for neonatal RBCs than for adult cells. To characterize material properties determining RBC deformability, we measured membrane extensional (shear) and bending elastic moduli, the time constant for elastic recovery from extensional deformation and hemoglobin viscosity (ie, cytoplasmic viscosity) of neonatal and adult RBCs. Membrane surface viscosity and time constant for recovery from bending deformation were calculated. The extensional and bending moduli of neonatal RBCs were slightly smaller (10% and 16%, respectively) compared with adult cells. This suggests that the static resistance of neonatal RBC membrane to deformation and failure in response to a given force is slightly smaller. The time constant for recovery from extensional deformation of neonatal RBCs was larger by 14%, compared with adult cells. The time constant for bending deformation related to the RBC diameter and surface area was increased by 18% in the neonates. Membrane surface viscosity and hemoglobin viscosity were similar for both cell types. These results indicate that the deformability and viscoelastic properties of neonatal RBCs deviate only slightly from those of adult RBCs and that the increased aspiration pressure of neonatal RBCs is solely due to their large size. Some of the specific deformation characteristics observed in this study (increased aspiration pressure, decreased resistance to elastic deformation) may contribute to the shortened life span of neonatal RBCs.

A developmentally stable chromatin structure in the human beta-globin gene cluster.

The DNase I-hypersensitive sites in the human embryonic beta-globin gene region have been mapped in erythroid-enriched fractions of disaggregated fetal livers, in adult nucleated red blood cells, and in fetal brain tissue. Our analysis of a region extending 11 kilobases (kb) 5' of the epsilon-globin gene reveals many minor nuclease-hypersensitive sites and one major site located 6.1 kb upstream of the epsilon-globin gene. All of these hypersensitive sites are erythroid-specific, and the major site is stable throughout erythroid development. As assayed by nuclear runoff transcription, little or no epsilon-globin gene expression is detectable in fetal or adult erythroid cells. Thus, the presence of the major hypersensitive site 5' of the epsilon-globin gene in both fetal and adult erythroid cells demonstrates that this site is not specifically correlated with transcription of the gene or with a particular stage of development. Rather, this site may reflect an early event in erythroid differentiation. In addition, DNase I has been used to probe the overall sensitivity of epsilon-globin chromatin in fetal erythroid cells. Our findings indicate that the epsilon-globin gene as well as the other genes in the beta-globin cluster reside within the chromatin domain that is more DNase I-sensitive than "bulk" chromatin.

Specificity of the monoclonal anti-I antibody (Hy)

In previous work we found that a monoclonal cold hemagglutinin from patient Hy strongly bound antigens contained in stage IV breast cancer sera. To infer the chemical structure of the antigens expressed in the cancer sera, we studied the specificity of the antibody (Hy). The antibody (Hy) had I specificity, based on agglutination scores with adult and cord red blood cells. The binding of the antibody to synthetic and milk oligosaccharides was determined using a solid phase enzyme immunoassay (EIA). The anti-I antibody (Hy) strongly bound LacNAc0-Me, LacNAc1→6Gal, LacNAcl→6 (LacNAc1→3)Gal, LacNAc-1→6αGalNAc, LacNAcl→3 LacNAc, and LacNAc, 0.05, 0.06, 0.09, 0.22, 0.35 and 0.75 m M giving 50% inhibition, respectively. The anti-I antibody (Hy), similar to the anti-I antibody (Ma), strongly bound LacNAcl→6Gal, but it differed from the anti-I antibody (Ma) in its cross-reactivity with the i sequence. The anti-I antibody (Hy) showed similar reactivities as the hybridoma monoclonal antibodies M18 and M39 with LacNAcl→6Gal and with the i-active sequence. The EIA procedure is a useful alternative to either radioimmunoassay or immunoprecipitation method in the study of anti-I,i specificities.

Erythrocyte Deformability in the Fetus, Preterm, and Term Neonate

Deformability of red blood cells (RBC) is an important determinant of microcirculation, of oxygen transport and release to the tissues, and of RBC life span. Deformability of RBC from five fetuses, 20 preterm infants, 20 term neonates, and 20 adults was determined by direct microscopic observation of RBC subjected to shear stresses of 6 to 85 dyn/cm2 using a counter-rotating rheoscope. There was no significant difference in deformability among RBC from the fetuses, the preterm and term neonates, and the adults at any shear stress. More than 95% of fetal, neonatal, and adult RBC were capable of tank-tread motion. Compared to adults, the frequency distribution of RBC deformability was slightly broader in the fetuses and neonates because of the presence of more highly and poorly deformable RBC. The increased number of rigid RBC may contribute to the shortened life span of fetal RBC.

Glutathione in the red blood cells of embryonic mice

1. 1. A micro-method for the determination of red blood cell glutathione levels has been developed. 2. 2. It has been shown that, in order to obtain true values of glutathione concentrations within red blood cells, it is necessary to correct for loss of labelled glutathione and also to take account of the time taken to complete the analytical procedure. 3. 3. Glutathione is the major small molecular weight thiol present in embryonic red blood cells. 4. 4. The glutathione to haemoglobin ratio is maintained at 0.6 from 13 days gestation to adulthood in the mouse. 5. 5. Decay of glutathione in both adult and embryonic red blood cells can be avoided by incubation of the red blood cells in glucose containing buffers.

Putative nuclear triiodothyronine receptors in tadpole erythrocytes during metamorphic climax.

The characteristics of the nuclear T3 receptors present in red blood cells (RBCs) of Rana catesbeiana tadpoles undergoing metamorphic climax have been investigated with a T3 saturation technique. Because there were significant amounts of receptor-bound endogenous hormone, prolonged incubation in vitro (48 h at 21 C) was necessary to achieve binding equilibrium. Receptor number, which averaged 783 +/- 35 (+/- SE) sites/nucleus during early prometamorphosis (stages XIV-XVI), increased rapidly during the subsequent stages of this phase. By stage XIX, receptor number had reached a maximum of 2464 +/- 152. During climax, receptor number decreased steadily, and by stage XXV, it was lower than that observed during premetamorphosis (stages V-X). This decrease was attributed to the replacement of larval RBCs, which have a high receptor content, by adult RBCs, which possess significantly fewer sites per nucleus. At midclimax, adult and larval RBCs were separated on a Renografin continuous density gradient. Adult cells constituted more than 65% of the total cell population and were shown to contain only 126 +/- 46 sites/nucleus. Although the striking increase in receptor number preceded the substantial increases in plasma T4 and T3 levels that occurred during climax, it was associated with a measurable increase in plasma thyroid hormone levels. Furthermore, receptor number in stage XIV tadpoles was increased markedly after immersion for 14 days in water containing sufficient T3 to raise plasma T3 only to levels normally observed in late prometamorphosis. These findings strongly support the hypothesis that the increases in receptor number and plasma thyroid hormone levels that occur before climax in this species are causally related.

Red blood cell aggregation in preterm and term neonates and adults.

Aggregation of red blood cells (RBC) is a major determinant of blood viscosity and of blood circulation through vessels with slow flow (i.e. veins). RBC aggregation and plasma fibrinogen were studied in placental blood samples from 25 neonates with 24 to 41 wk of gestation and in blood from 13 normal adults. The rate and final extent of RBC aggregation were measured by means of a rheoscope (increase in light transmission during blood stasis). Both the rate and extent of RBC aggregation were low in the premature infants, increased with gestational age, and reached the highest values in the adults. Blood from seven infants with 24 to 28 wk of gestation did not show any significant RBC aggregation during the first minute of stasis. RBC aggregation was closely related to the fibrinogen level. Cross-suspension studies (neonatal RBC in adult plasma and adult RBC in neonatal plasma) showed that neonatal and adult RBC had the same aggregation pattern when they were suspended in the same plasma. Moreover, neonatal and adult RBC demonstrated the same strong aggregation when they were resuspended in 1% dextran. These results indicate that specific plasma properties are responsible for the decreased RBC aggregation observed in the neonates while their specific RBC properties do not affect RBC aggregation.

Increase in 3,5,3'-triiodothyronine (T3)-binding sites in tadpole erythrocyte nuclei during spontaneous and T3-induced metamorphosis.

The change in T3-binding sites in larval and adult type red blood cell (RBC) nuclei during metamorphosis was studied with the use of Scatchard plots. The number of binding sites per nucleus or the maximum binding capacity (MBC) in the larval type RBC (containing larval hemoglobins) increased from 240 at stage X to 410 at stage XVIII. The apparent Kd also increased from 170 pM at stage X to 260 pM at stage XVIII. At stages XX-XXI, adult type RBCs (containing adult hemoglobins) accounted for 22% of the RBC population. At stage XXII, adult RBCs increased to 54%. In the separated larval and adult RBCs from stage XXII, obtained by Percoll gradient centrifugation, the MBC in larval RBCs had increased to 930 sites/nucleus, a 4-fold increase over stage X, with a Kd of 760 pM; adult RBCs had 1150 sites/nucleus and a Kd of 1530 pM. In contrast, when T3 binding was measured in the whole RBC population from stage XXII tadpoles, the MBC and Kd in larval and adult RBC were estimated at 780 sites/nucleus with a Kd of 640 pM and 1200 sites/nucleus with Kd of 2300 pM, respectively. After metamorphosis, the larval RBCs disappeared and were replaced by adult RBCs. The MBC in adult RBC had declined to 350 sites/nucleus at stage XXV (froglet). The Kd of adult RBC decreased to 790 pM at stage XXV. When stage XVII tadpoles were given a single injection of T3, a 2-fold increase in MBC and Kd was observed after 14 days at 20 C. The values observed for T3-treated animals (870 sites/nucleus with a Kd of 660 pM) were close to the values for the larval RBCs at stage XXII in spontaneous metamorphosis. The MBC and apparent dissociation constant of control animals (400 sites/nucleus; Kd of 270 pM) were almost the same as at stage XVIII in spontaneous metamorphosis. Treatment with PRL (10 micrograms/10 g tadpole every 2 days) had no effect on the T3-binding sites of RBC nuclei. This dose is adequate to stimulate tail fin growth and inhibit hind limb growth. The same dose of PRL did not affect the T3-induced increase in the MBC and Kd of the T3-binding sites. The results are discussed in terms of the positive regulation of the number of T3 receptors by thyroid hormones. The metamorphic response in amphibia appears to require an increase in the number of T3-binding sites (Receptor Induction).

A comparison of two procedures useful for the isolation of Hb F from adult red blood cells and for the quantitation of the types of μ chain by high-performance liquid chromatography

Two methods have been used to isolate Hb F from red cells with low levels of Hb F (<2% F AD), namely an alkali denturation procedure, as described by Tsuchiya et al. [ Dokkyo J. Med. Sci., 10 (1983) 13], and anion-exchange chromatography. Analyses of these Hb F enriched hemoglobin solutions by high-performance liquid chromatography allowed quantitation of the different γ chains in the Hb F. Although the data showed considerable variation, particularly for samples with low levels of Hb F, the final results obtained with the two approaches were comparable, suggesting that the much simpler and more economical alkali denaturation procedure can be used for this purpose.

Oxygen equilibrium of larval and adult hemoglobins of the salamander, Pleurodeles walt II

1. 1. Larval red blood cells exhibited a higher oxygen affinity and a lower cooperativity than adult red blood cells. 2. 2. The Bohr effect was found equal to zero for the larval red blood cells. 3. 3. The two main fractions Hb A and Hb B found in adult red blood cells have different oxygen affinities and DPG effect, but the same normal cooperativity, and the same Bohr effect, slightly positive and “reverse” in comparison to that of mammalian hemoglobins.

Red blood cell-bound C3d in normal subjects and in random hospital patients.

Red blood cells (RBC) drawn into EDTA from 103 normal adults, 26 newborn infants, and 203 randomly selected hospital patients, and into citrate-phosphate-dextrose (CPD) from 87 Red Cross donors, were evaluated for RBC-bound C3d by agglutination with anti-C3d and by a radiolabeled anti-antiglobulin technique. Positive agglutination reactions were observed only with RBC from 26 hospital patients; however, by the radiolabeled antiglobulin method, C3d was demonstrable on all RBC, but its amount varied widely among different subjects. A normal range for RBC-bound C3d was established. RBC-bound C3d levels were not related to the age (18-88 years) or sex of the subjects and remained unchanged over 9 months. Red blood cells taken into CPD had more RBC-bound C3d than cells taken into EDTA; cord RBC had less than adult RBC. In 39 percent of the hospital patients (excluding those with autoimmune hemolytic anemia) RBC-bound C3d was above the normal range and a good correlation was found between values obtained by the radiolabeled anti-antiglobulin method and by agglutination titration scores. There was a threshold level of RBC-bound C3d below which agglutination reactions were negative. Evaluation of RBC-bound C3d in health and disease is important for determining optimal characteristics of anticomplement antiglobulin reagents.

Detection of fetal hemorrhage in Rh immune globulin candidates. A rosetting technique using enzyme-treated Rh2Rh2 indicator erythrocytes.

Current serologic tests occasionally fail to identify women needing more than one vial of Rh immune globulin. We compared the indirect antiglobulin test after incubation with anti-D and a rosetting technique using enzyme treated Rh2Rh2 erythrocytes as methods for identifying significant fetal maternal hemorrhage (FMH). Artificial mixtures containing 0.05 to 1.2 percent Rh1rh (CcDe) fetal red blood cells mixed with rh (ce) adult red blood cells were tested. The indirect antiglobulin test of the 0.6 percent mixture (approximately 30 ml FMH) was reported to be microscopically positive by 17/20 technologists; whereas, 20/20 found the rosetting test to be strongly positive. The volume of FMH in 118 postpartum Rh immune globulin candidates was quantified using Kleihauer's test and formula. The results of the rosetting and Kleihauer tests of blood specimens from these patients were negative 1.4 ml for two, and strongly positive rosetting test and FMH of 6.5 ml for one. The rosetting test utilizes routine blood banking skills and requires 5 minutes more "hands on" time than an indirect antiglobulin test. Confirmation and quantification of positive results by an acid-elution test is necessary.

Detection and quantitation of fetal maternal hemorrhage utilizing an enzyme-linked antiglobulin test.

Existing methods to evaluate fetal-maternal hemorrhage depend upon red blood cell agglutination or blood film elution techniques. These tests are insensitive and difficult to quantitate and reproduce. An enzyme-linked antiglobulin test was evaluated to determine its suitability for clinical testing of postpartum candidates for Rh immune globulin administration. Prepared mixtures of Rh positive fetal and Rh negative adult red blood cells approximating fetal maternal hemorrhage ratios of 0-2.0 percent were studied. In 43 assays, the enzyme-linked antiglobulin test consistently detected Rh positive fetal red blood cells in the 0.5 and 0.25 percent mixtures representing a 25 ml and a 12.5 ml hemorrhage, respectively, in a 70-kg woman. The 0.125 percent red blood cell suspension was positive in 85 percent of the assays and the 0.0625 percent suspension was positive in 56 percent of the tests. Agglutination testing by Du variant technique failed to detect 25 percent of the 0.5 percent mixtures. Only 45 percent of tests with the Rh immune globulin crossmatch detected the 0.5 percent mixture. A modified Kleihauer-Betke procedure was as sensitive, but less reproducible than the enzyme-linked antiglobulin test. Forty-seven Rh immune globulin candidates were studied to assess the quantity of fetal maternal hemorrhage. Fourteen patients (29.8%) had detectable Rh positive red blood cells by enzyme-linked antiglobulin tests but all hemorrhages were less than 12 ml; agglutination tests did not detect any fetal red blood cells. We conclude that the enzyme-linked antiglobulin test is a simple, sensitive, and objective procedure for detecting small amounts of Rh positive red blood cells in Rh negative blood and should be applicable to clinical testing of post-partum Rh immune globulin candidates.

Deformability of Density Separated Red Blood Cells in Normal Newborn Infants and Adults

The deformability of neonatal and adult red blood cells (RBC) was studied using both unseparated and density (i.e., age) fractionated RBC. Blood samples were obtained from 10 normal newborn infants (placental blood) and 10 adults. Deformability was measured by direct microscopic observation of RBC subjected to shear stresses of 2.5-500 dynes/cm2 using a counter-rotating Rheoscope. There was no significant difference in deformability between unseparated neonatal and adult RBC at any shear stress. The 3% least dense ("youngest") RBC showed significantly decreased hemoglobin concentrations (MCHC), increased volumes (MCV) and elevated deformability at any shear stress when compared to the 3% most dense ("oldest") cells, with the values for the unseparated RBC lying between these two extremes. The least dense neonatal RBC had a significantly lower MCHC and higher deformability than the least dense adult cells; however, the most dense neonatal RBC had lost more volume than the adult cells (33 versus 17%), had a higher MCHC, and were less deformable than the most dense adult cells. This indicates that the accelerated decrease in deformability of aging neonatal RBC is related to the more pronounced increase in MCHC, which is the principal determinant of the internal viscosity of the RBC.

Chemical and immunological characterization of developmentally expressed chicken erythroid surface membrane antigens

The expression of two hematopoietic-lymphoid membrane antigens, referred to as chicken fetal antigen (CFA) and chicken adult antigen (CAA) were investigated on primitive and definitive peripheral red blood cells (RBC) from different-aged chickens using chemical and immunological techniques. Differential adsorptions of antisera specific for adult RBC membrane antigens permitted the serological dissection of CAA into eight antigenic determinants. CFA and CAA were assayed by hemagglutination, hemolysis, and immune precipitation of radioiodinated surface antigens of RBC from different-aged chickens. Primitive RBC express CFA, while definitive RBC express three distinct phenotypes: CFA, both CFA and CAA, or CAA, depending on the developmental age of the chicken from which the RBC were obtained. When solubilized membrane extracts of radioiodinated peripheral RBC from chickens at 5 and 18 days embryonic development (E5 and E18, respectively), 13 days posthatch development (H13), and adult chickens were immunoprecipitated and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the major antigen detected by anti-CFA sera was associated with proteins having apparent molecular weights ( M r) of 50,000 daltons (50 kd). The antigens detected by anti-CAA sera were associated with proteins having apparent M r of 102, 81, 48, and 43 kd.