Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child

BACKGROUND

When thyroid deficiency occurs simultaneously in a pregnant woman and her fetus, the child's neuropsychological development is adversely affected. Whether developmental problems occur when only the mother has hypothyroidism during pregnancy is not known.

METHODS

In 1996 and 1997, we measured thyrotropin in stored serum samples collected from 25,216 pregnant women between January 1987 and March 1990. We then located 47 women with serum thyrotropin concentrations at or above the 99.7th percentile of the values for all the pregnant women, 15 women with values between the 98th and 99.6th percentiles, inclusive, in combination with low thyroxine levels, and 124 matched women with normal values. Their seven-to-nine-year-old children, none of whom had hypothyroidism as newborns, underwent 15 tests relating to intelligence, attention, language, reading ability, school performance, and visual-motor performance.

RESULTS

The children of the 62 women with high serum thyrotropin concentrations performed slightly less well on all 15 tests. Their full-scale IQ scores on the Wechsler Intelligence Scale for Children, third edition, averaged 4 points lower than those of the children of the 124 matched control women (P= 0.06); 15 percent had scores of 85 or less, as compared with 5 percent of the matched control children. Of the 62 women with thyroid deficiency, 48 were not treated for the condition during the pregnancy under study. The full-scale IQ scores of their children averaged 7 points lower than those of the 124 matched control children (P=0.005); 19 percent had scores of 85 or less. Eleven years after the pregnancy under study, 64 percent of the untreated women and 4 percent of the matched control women had confirmed hypothyroidism.

CONCLUSIONS

Undiagnosed hypothyroidism in pregnant women may adversely affect their fetuses; therefore, screening for thyroid deficiency during pregnancy may be warranted.

Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study

The aim of this study was to test the hypothesis that individual differences in the response of maximal O(2) uptake (VO(2max)) to a standardized training program are characterized by familial aggregation. A total of 481 sedentary adult Caucasians from 98 two-generation families was exercise trained for 20 wk and was tested for VO(2max) on a cycle ergometer twice before and twice after the training program. The mean increase in VO(2max) reached approximately 400 ml/min, but there was considerable heterogeneity in responsiveness, with some individuals experiencing little or no gain, whereas others gained >1.0 l/min. An ANOVA revealed that there was 2.5 times more variance between families than within families in the VO(2max) response variance. With the use of a model-fitting procedure, the most parsimonious models yielded a maximal heritability estimate of 47% for the VO(2max) response, which was adjusted for age and sex with a maternal transmission of 28% in one of the models. We conclude that the trainability of VO(2max) is highly familial and includes a significant genetic component.

The effect of sex, age and race on estimating percentage body fat from body mass index: The Heritage Family Study

OBJECTIVE

To study the effects of sex, age and race on the relation between body mass index (BMI) and measured percent body fat (%fat).

DESIGN

Cross-sectional validation study of sedentary individuals.

SUBJECTS

The Heritage Family Study cohort of 665 black and white men and women who ranged in age from 17 to 65 y.

MEASUREMENTS

Body density determined from hydrostatic weighing. Percentage body fat determined with gender and race-specific, two-compartment models. BMI determined from height and weight, and sex and race in dummy coded form.

RESULTS

Polynomial regression showed that the relationship between %fat and BMI was quadratic for both men and women. A natural log transformation of BMI adjusted for the non-linearity. Test for homogeneity of log transformed BMI and gender showed that the male-female slopes were within random variance, but the intercepts differed. For the same BMI, the %fat of females was 10.4% higher than that of males. General linear models analysis of the women's data showed that age, race and race-by-BMI interaction were independently related to %fat. The same analysis applied to the men's data showed that %fat was not just a function of BMI, but also age and age-by-BMI interaction. Multiple regression analyses provided models that defined the bias.

CONCLUSIONS

These data and results published in the literature show that BMI and %fat relationship are not independent of age and gender. These data showed a race effect for women, but not men. The failure to adjust for these sources of bias resulted in substantial differences in the proportion of subjects defined as obese by measured %fat.

Neuronal cell Thy-1 glycoprotein: homology with immunoglobulin

The amino acid sequences of mouse brain Thy-1 glycoproteins are shown to be homologous to those of variable-region immunoglobulin domains. There is also good homology with constant domains and beta 2-microglobulin; overall the results suggest that Thy-1 may be like the primordial immunoglobulin domain. Preliminary evidence for an invertebrate Thy-1 homolog supports this possibility.

Cloning and expression of the rat prolactin receptor, a member of the growth hormone/prolactin receptor gene family

The primary structure of the rat liver prolactin receptor has been deduced from a single complementary DNA clone. The sequence begins with a putative 19 amino acid signal peptide followed by the 291 amino acid receptor that includes a single 24 amino acid transmembrane segment. In spite of the fact that the prolactin receptor has a much shorter cytoplasmic region than the growth hormone receptor, there is strong localized sequence identity between these two receptors in both the extracellular and cytoplasmic domains, suggesting that the two receptors originated from a common ancestor.

Familial resemblance for VO2max in the sedentary state: the HERITAGE family study

This study investigates the familial resemblance of maximal oxygen uptake (VO2max) based on data from 86 nuclear families of Caucasian descent participating in the HERITAGE Family Study. In the current study, VO2max was measured twice on a cycle ergometer in 429 sedentary individuals (170 parents and 259 of their offspring), aged between 16 and 65 yr. The VO2max was adjusted by regression procedures for the effects of 1) age and sex; 2) age, sex, and body mass; and 3) age, sex, body mass, fat mass, and fat-free mass, as determined by underwater weighing. Evidence for significant familial resemblance was observed for each of the three VO2max phenotypes. Spouse, sibling, and parent-offspring correlations were significant, suggesting that both genetic and environmental factors contribute to the familial resemblance for VO2max. Maximal heritability estimates were at least 50%, a value inflated to an undetermined degree by nongenetic factors. The hypothesis of maternal inheritance, with the father's contribution being environmental, was also found to fit the data with estimates of maternal heritability, potentially associated in part with mitochondrial inheritance, reaching about 30%. These results suggest that genetic and nongenetic factors as well as maternal influences contribute to the familial aggregation of VO2max in sedentary individuals.

Race, visceral adipose tissue, plasma lipids, and lipoprotein lipase activity in men and women: the Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) family study

Abdominal obesity is associated with numerous metabolic alterations, such as hypertriglyceridemia and low levels of high density lipoprotein (HDL) cholesterol. However, compared with abdominally obese white individuals, abdominally obese black individuals have been characterized by higher plasma HDL cholesterol levels, suggesting that the impact of abdominal fat accumulation on the lipoprotein-lipid profile may differ among ethnic groups. Therefore, we have compared the associations between body fatness, visceral adipose tissue (AT) accumulation, and metabolic risk variables in a sample of 247 white men and 240 white women versus a sample of 93 black men and 143 black women. Although no difference in mean total body fatness was found between the 2 race groups, white men had higher levels of visceral AT than did black men (P<0.001). Despite the fact that black women had a greater body fat content than did white women, black women had levels of visceral AT that were similar to those of white women, suggesting a lower susceptibility to visceral obesity in black women. This lower accumulation of visceral AT in blacks was accompanied by significantly reduced apolipoprotein B concentrations and ratios of total cholesterol to HDL cholesterol as well as higher plasma HDL cholesterol levels (P<0.05) compared with those values in whites. Irrespective of sex, higher postheparin plasma hepatic lipase (HL) and lower lipoprotein lipase (LPL) activities were found in whites, resulting in an HL/LPL ratio that was twice as high in whites as in blacks (P<0.005). Although differences in lipoprotein-lipid levels were noted between whites and blacks, results from multiple regression analyses revealed that after control for morphometric and metabolic variables of the study (body fat mass, visceral AT, LPL, HL, and age), ethnicity had, per se, only a minor contribution to the variance in plasma lipoprotein levels. Thus, our results suggest that the higher plasma HDL cholesterol levels and the generally more cardioprotective plasma lipoprotein profile found in abdominally obese black versus white individuals are explained, at least to a certain extent, by a lower visceral AT deposition and a higher plasma LPL activity in black individuals.

A controlled trial of corticosteroid injections into facet joints for chronic low back pain

BACKGROUND

Chronic low back pain is a common problem with many treatments, few of which have been rigorously evaluated. This randomized, placebo-controlled trial was designed to evaluate the efficacy of injections of corticosteroid into facet joints to treat chronic low back pain.

METHODS

Patients with chronic low back pain who reported immediate relief of their pain after injections of local anesthetic into the facet joints between the fourth and fifth lumbar vertebrae and the fifth lumbar and first sacral vertebrae were randomly assigned to receive under fluoroscopic guidance injections of either methylprednisolone acetate (20 mg; n = 49) or isotonic saline (n = 48) in the same facet joints. Ninety-five patients were followed for six months and their condition assessed with scales of pain severity, back mobility, and limitation of function.

RESULTS

After one month, none of the outcome measures evaluating pain, functional status, and back flexion differed clinically or statistically between the two study groups. Forty-two percent of the patients who received methylprednisolone and 33 percent of those who received placebo reported marked or very marked improvement (95 percent confidence interval for the difference, -11 to 28 percentage points; P = 0.53). The results were similar after three months. At the six-month evaluation, the patients treated with methylprednisolone reported more improvement, less pain on the visual-analogue scale, and less physical disability. The differences were reduced, however, when concurrent interventions were taken into account. Moreover, only 11 patients (22 percent) in the methylprednisolone group and 5 (10 percent) in the placebo group had sustained improvement from the first month to the sixth month (95 percent confidence interval for the difference, -2 to 26; P = 0.19).

CONCLUSIONS

We conclude that injecting methylprednisolone acetate into the facet joints is of little value in the treatment of patients with chronic low back pain.

Squash trypsin inhibitors from Momordica cochinchinensis exhibit an atypical macrocyclic structure

Three trypsin inhibitors (TIs), from the seeds of the squash Momordica cochinchinensis (MCo), have been isolated and purified using gel filtration, ion exchange chromatography, and reverse-phase HPLC. Their sequences could be determined only after proteolytic cleavages. In the case of MCoTI-I and -II, it was shown that their polypeptide backbones are cyclic, a structure that has never been described in squash TIs. They contain 34 amino acid residues with 3 disulfide bridges and measured molecular masses of 3453.0 and 3480.7, respectively. They are the largest known macrocyclic peptides containing disulfide bridges. Their sequences show strong homology to other squash TIs, suggesting a similar three-dimensional structure and an analogous mechanism of action. A model of MCoTI-II was constructed by analogy to the crystal structure of the complex between bovine trypsin and CMTI-I, indicating that the linker connecting the two termini is flexible and does not impose significant geometrical constraints. This flexibility allows an Asp-Gly peptide bond rearrangement to occur in this region, giving rise to two isoforms of MCoTI-II. Although the importance of cyclization is not clear, it might confer increased stability and resistance to proteolysis. A minor species, MCoTI-III, was also characterized as containing 30 amino acid residues with a molecular mass of 3379.6. This component possesses a linear backbone with a blocked N-terminus. MCoTIs represent interesting candidates for drug design, either by changing their specificity of inhibition or by using their structure as natural scaffolds bearing new binding activities.

Ovalbumin: a secreted protein without a transient hydrophobic leader sequence

Ovalbumin mRNA was translated in a reticulocyte lysate. The primary translation product starts with methionine derived from Met-tRNAf. When the nascent polypeptide is about 20 residues long, this methionine is removed. The new NH2-terminal glycine is acetylated from acetyl-CoA when the polypeptide is 44 residues long. The sequence of 35 residues at the NH2 terminus of ovalbumin was determined by automated Edman degradation after a method was devised to prevent acetylation during protein synthesis in the reticulocyte lysate. This sequence is the same as that of secreted ovalbumin and does not resemble the transient "signal peptides" associated with most secretory proteins, including three other egg white proteins synthesized in the same cells as ovalbumin.

Prevalence of AIDS-related risk factors and condom use in the United States

A national probability survey of human immunodeficiency virus (HIV)-related risk factors among the general heterosexual population, the National AIDS (acquired immunodeficiency syndrome) Behavioral Surveys, has obtained data from 10,630 respondents. Data are presented on the prevalence of HIV-related risks in the general heterosexual population, on the distribution of the three largest risk groups across social strata, and on the prevalence and distribution of condom use among heterosexuals reporting a risk factor. Between 15 and 31 percent of heterosexuals nationally and 20 and 41 percent in cities with a high prevalence of AIDS reported an HIV risk factor. Condom use was relatively low. Only 17 percent of those with multiple sexual partners, 12.6 percent of those with risky sexual partners, and 10.8 percent of untested transfusion recipients used condoms all the time. Overall, the results suggest that current HIV prevention programs have, to a very limited extent, reached those heterosexuals with multiple sexual partners but have failed to reach many other groups of the heterosexual population at risk for HIV. New public health strategies may be needed for these specific risk groups.

Rat brain Thy-1 glycoprotein. The amino acid sequence, disulphide bonds and an unusual hydrophobic region

The full sequence of the Thy-1 membrane glycoprotein of rat brain is reported. The sequence was determined from tryptic and V-8 proteinase peptides and consisted of 111 amino acids. The amino terminus was blocked and consisted of a pyroglutamic acid residue. The molecule contained two disulphide bonds, namely Cys-9--Cys-111 and Cys-19--Cys-85. Three N-linked amino sugars were located at Asn-23, Asn-74 and Asn-98. In each case the sequence on the C-terminal side of the attachment point was Asn-Xaa-Thr as would be expected for N-linkage. The C-terminal peptides were unusual, in that they were either obtained in a highly aggregated form, or could only be purified after binding to Brij 96 micelles. Thus they appeared to have hydrophobic properties, yet did not contain any extended sequence of hydrophobic amino acids. Other unusual features of the C-terminal peptides were the presence of unidentified ninhydrin-positive material and of glucosamine and galactosamine. The C-terminal residue has not been directly identified but Cys-111 is the last conventional amino acid. It is suggested that the hydrophobic properties of the C-terminal peptides may be due to the linkage of lipid. The sequence of the Thy-1 glycoprotein showed homologies with immunoglobulin domains. This relationship is examined in detail in the paper following [Cohen et al. (1981) Biochem. J. 193, 000--000].

Effects of endurance exercise training on plasma HDL cholesterol levels depend on levels of triglycerides: evidence from men of the Health, Risk Factors, Exercise Training and Genetics (HERITAGE) Family Study

High density lipoprotein (HDL) cholesterol concentrations have been shown to increase with regular endurance exercise and, therefore, can contribute to a lower risk of coronary heart disease in physically active individuals compared with sedentary subjects. Although low HDL cholesterol levels are frequently observed in combination with hypertriglyceridemia, some individuals may be characterized by isolated hypoalphalipoproteinemia, ie, low HDL cholesterol levels in the absence of elevated triglyceride (TG) concentrations. The present study compared the responses of numerous lipoprotein-lipid variables to a 20-week endurance exercise training program in men categorized on the basis of baseline TG and HDL cholesterol concentrations: (1) low TG and high HDL cholesterol (normolipidemia), (2) low TG and low HDL cholesterol (isolated low HDL cholesterol), (3) high TG and high HDL cholesterol (isolated high TGs), and (4) high TGs and low HDL cholesterol (high TG/low HDL cholesterol). A series of physical and metabolic variables was measured before and after the training program in a sample of 200 men enrolled in the Health, Risk Factors, Exercise Training and Genetics (HERITAGE) Family Study. At baseline, men with high TG/low HDL cholesterol had more visceral adipose tissue than did men with isolated low HDL cholesterol and men with normolipidemia. The 0.4% (not significant) exercise-induced increase in HDL cholesterol levels in men with isolated low HDL cholesterol suggests that they did not benefit from the "HDL-raising" effect of exercise. In contrast, men with high TG/low HDL cholesterol showed a significant increase in HDL cholesterol levels (4.9%, P<0.005). Whereas both subgroups of men with elevated TG levels showed reductions in plasma TGs ( approximately -15.0%, P<0.005), only those with high TG/low HDL cholesterol showed significantly reduced apolipoprotein B levels at the end of the study (-6.0%, P<0.005). Multiple regression analyses revealed that the exercise-induced change in abdominal subcutaneous adipose tissue (10.6%, P<0.01) was the only significant correlate of the increase in plasma HDL cholesterol with training in men with high TG/low HDL cholesterol. Results of the present study suggest that regular endurance exercise training may be particularly helpful in men with low HDL cholesterol, elevated TGs, and abdominal obesity.

Identification of an obesity quantitative trait locus on mouse chromosome 2 and evidence of linkage to body fat and insulin on the human homologous region 20q

Chromosomal synteny between the mouse model and humans was used to map a gene for the complex trait of obesity. Analysis of NZB/BINJ x SM/J intercross mice located a quantitative trait locus (QTL) for obesity on distal mouse chromosome 2, in a region syntenic with a large region of human chromosome 20, showing linkage to percent body fat (likelihood of the odds [LOD] score 3.6) and fat mass (LOD score 4.3). The QTL was confirmed in a congenic mouse strain. To test whether the QTL contributes to human obesity, we studied linkage between markers located within a 52-cM region extending from 20p12 to 20q13.3 and measures of obesity in 650 French Canadian subjects from 152 pedigrees participating in the Quebec Family Study. Sib-pair analysis based on a maximum of 258 sib pairs revealed suggestive linkages between the percentage of body fat (P < 0.004), body mass index (P < 0.008), and fasting insulin (P < 0.0005) and a locus extending approximately from ADA (the adenosine deaminase gene) to MC3R (the melanocortin 3 receptor gene). These data provide evidence that a locus on human chromosome 20q contributes to body fat and insulin in a human population, and demonstrate the utility of using interspecies syntenic relationships to find relevant disease loci in humans.

Age, sex, race, initial fitness, and response to training: the HERITAGE Family Study

Effects of age, sex, race, and initial fitness on training responses of maximal O(2) uptake (VO(2 max)) are unclear. Data were available on 435 whites and 198 blacks (287 men and 346 women), aged 17-65 yr, before and after standardized cycle ergometer training. Individual responses varied widely, but VO(2 max) increased significantly for all groups. Responses by men and women and by blacks and whites of all ages varied widely. There was no sex difference for change (Delta) in VO(2 max) (ml. kg(-1). min(-1)); women had lower initial values and greater relative (%) increases. Blacks began with lower values but had similar responses. Older subjects had a lower Delta but a similar percent change. Baseline VO(2 max) correlated nonsignificantly with DeltaVO(2 max) but significantly with percent change. There were high, medium, and low responders in all age groups, both sexes, both races, and all levels of initial fitness. Age, sex, race, and initial fitness have little influence on VO(2 max) response to standardized training in a large heterogeneous sample of sedentary black and white men and women.

The tyrosine kinase substrate eps15 is constitutively associated with the plasma membrane adaptor AP-2

The ubiquitous eps15 protein was initially described as a substrate of the EGF receptor kinase. Its functions are not yet delineated and this work provides evidence for its possible role in endocytosis. A novel anti-eps15 antibody, 6G4, coimmunoprecipitated proteins of molecular mass 102 kD. In human cells, these proteins were identified as the alpha- and beta-adaptins of the AP-2 complex on the basis of their NH2-terminal sequence and their immunoreactivity with anti-alpha- and anti-beta-adaptin antibodies but not with anti-gamma-adaptin antibody. In addition, the anti-eps15 antibody coimmunoprecipitated metabolically labeled polypeptides with molecular mass of 50 and 17 kD, comparable to those of the two other components of the AP-2 complex, mu2 and sigma 2. Constitutive association of eps15 with AP-2 was confirmed by two sets of experiments. First, eps15 was detected in immunoprecipitates of anti-alpha- and anti-beta-adaptin antibodies. Second, alpha- and beta- but not gamma-adaptins were precipitated by a glutathione-S-transferase eps15 fusion protein. The association of eps15 with AP-2 was ubiquitous and conserved between species, since it was observed in human lymphocytes and epithelial cells and in murine NIH3T3 fibroblasts. Our results are in keeping with a recent study showing homology between the NH2-terminal domains of eps15 and the product of the gene END3, involved in clathrin-mediated endocytosis of the pheromone alpha factor in Saccharomyces cerevisiae, and suggest a possible role for eps15 in clathrin-mediated endocytosis in mammals.

Acute and chronic effects of exercise on leptin levels in humans

The acute (single bout of exercise) and chronic (exercise training) effects of exercise on plasma leptin were investigated in 97 sedentary adult men (n = 51) and women (n = 46) participating in the HERITAGE Family Study. Exercise training consisted of a standardized 20-wk endurance training program performed in the laboratory on a computer-controlled cycle ergometer. Maximal oxygen uptake, body composition assessed by hydrostatic weighing, and fasting insulin level were also measured before and after training. Pre- and posttraining blood samples were obtained before and after completion of a maximal exercise test on the cycle ergometer. Exercise training resulted in significant changes in maximal oxygen uptake (increase in both genders) and body composition (reduction of fat mass in men and increase in fat-free mass in women). There were considerable interindividual differences in the leptin response to acute and chronic effects of exercise, some individuals showing either increase or reduction in leptin, others showing almost no change. On average, leptin levels were not acutely affected by exercise. After endurance training was completed, leptin levels decreased significantly in men (from 4.6 to 3.9 ng/ml; P = 0.004) but not in women. However, after the training-induced changes in body fat mass were accounted for, the effects of exercise training were no longer significant. Most of the variation observed in leptin levels after acute exercise or endurance training appears to be within the confidence intervals of the leptin assay. We conclude that there are no meaningful acute or chronic effects of exercise, independent of the amount of body fat, on leptin levels in humans.

Abdominal visceral fat is associated with a BclI restriction fragment length polymorphism at the glucocorticoid receptor gene locus

Several investigations have suggested that body fat distribution is influenced by nonpathologic variations in the responsiveness to cortisol. Genetic variations in the glucocorticoid receptor (GRL) could therefore potentially have an impact on the level of abdominal fat. A restriction fragment length polymorphism (RFLP) has previously been detected with the BclI restriction enzyme in the GRL gene identifying two alleles with fragment lengths of 4.5 and 2.3 kb. This study investigates whether abdominal fat areas measured by computerized tomography (CT) are associated with this polymorphism in 152 middle-aged men and women. The less frequent 4.5-kb allele was found to be associated with a higher abdominal visceral fat (AVF) area independently of total body fat mass (4.5/4.5 vs. 2.3/2.3 kb genotype; men: 190.7 +/- 30.1 vs. 150.7 +/- 33.3 cm2, p = 0.04; women: 132.7 +/- 37.3 vs. 101.3 +/- 34.5 cm2, p = 0.06). However, the association with AVF was seen only in subjects of the lower tertile of the percent body fat level. In these subjects, the polymorphism was found to account for 41% (p = 0.003) and 35% (p = 0.007), in men and women, respectively, of the total variance in AVF area. The consistent association between the GRL polymorphism detected with BclI and AVF area suggests that this gene or a locus in linkage disequilibrium with the BclI restriction site may contribute to the accumulation of AVF.

The primary structure of the beta-subunit of the cell surface adhesion glycoproteins LFA-1, CR3 and p150,95 and its relationship to the fibronectin receptor

The lymphocyte-function-associated antigen-1 (LFA-1), the complement receptor type 3 (CR3) and the antigen p150,95 are cell-surface glycoproteins. They are heterodimeric complexes, each containing a unique alpha-subunit noncovalently associated with a common beta-subunit. We have purified the beta-subunit from human spleen and obtained limited peptide sequences. What appears to be the complete primary structure for the fully processed beta-subunit was obtained by cDNA sequencing of clones from a phorbol ester (PMA) stimulated U937 cDNA library. There are five possible glycosylation sites and a transmembrane segment. The sequence contains a high level of cysteine (7.6%), with 24 of the 57 cysteine residues being found in three repeating units each with eight residues. The entire primary structure has 47% identity to a subunit of a fibronectin binding protein from chicken fibroblasts. It seems that LFA-1, CR3 and p150,95 antigens may belong to an extended family of cell surface molecules including the fibronectin binding protein.

Peptide and nucleotide sequences of rat CD4 (W3/25) antigen: evidence for derivation from a structure with four immunoglobulin-related domains

The rat W3/25 antigen was the first marker antigen of helper T lymphocytes to be identified. Subsequently, the human OKT4 antigen (now called CD4) was described, and cell distribution and functional data suggested that W3/25 and OKT4 antigens were homologous. This is now confirmed by the matching of peptide sequences from W3/25 antigen with sequence predicted from rat cDNA clones detected by cross-hybridization with a cDNA probe for human CD4. Analysis of the two sequences suggests an evolutionary origin from a structure with four immunoglobulin-related domains, although only domain 1 at the NH2 terminus meets the standard criteria for an immunoglobulin-related sequence. CD4 domains 2 and 4 contain disulfide bonds but seem like truncated immunoglobulin domains, whereas domain 3 may have a pattern of beta-strands like an immunoglobulin variable domain, but without the disulfide bond.