An algorithm to analyse the hydrolysis pathway of peptides and proteins by sequence analyses of unfractionated digestion mixtures

We have designed and implemented on a personal computer a program for identifying and quantifying the fragments present in a peptide mixture obtained by hydrolysing a polypeptide of known sequence using digesting agents. The qualitative data utilized by the main algorithm consist of the target sequence of the intact molecule and the amino acid residues identified at each step of the automatic sequence analysis of the unfractionated digestion mixture. In this way, the sequence of each fragment present in the mixture is quickly reconstructed. Furthermore, if the quantitative data of the amino acid residues identified at each step of the sequence analysis are utilized, the program will correlate the sequence of each fragment to its amount. We furnish an example of the application intended for the rapid identification and characterization of the extracellular proteinases produced by a basidiomycete fungus, utilizing the bovine insulin beta-chain as target substrate. A variety of uses for the method are discussed.

Cytokine production pathway in the elderly

It is well known that aging is associated with various alterations in lymphoid cell functions, particularly with a progressive decline in immune responsiveness to exogenous antigens and increasing incidence of autoimmune phenomena. Many studies have been focused on the mechanisms of the immunologic features of aging. this review describes our results of studies performed to determine the influence of age on the capacity to produce interleukin-2 (IL-2), interferon-gamma (IFN-gamma), interleukin-4 (IL-4), interleukin-t (IL-5), interleukin-6 (IL-6) and tumor necrosis factor (TNF). Mitogen-stimulated cultures of mononuclear cells (MNC) from human beings were assessed for cytokine-producing capacity. A significant decrease in IFN-gamma and IL-2 production by MNC cultures from elderly individuals was observed. No significant difference was instead observed between cultures from elderly individuals and those from young ones as regards TNF-alpha, IL-4 and IL-6 production. Mitogen or antigen-stimulated cultures of MNC from aged mice also displayed a significant decrease in IFN-gamma and IL-2 production as well as TNF-beta. Instead IL-4 and IL-5 production significantly increased in these cultures. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in the elderly, i.e. a normal or increased humoral response (including autoimmune responses) in face of a low T cell immune responsiveness.

Characterization of extracellular proteases from Trametes trogii

The peptidase activities excreted in culture broths of Trametes trogii mycelium have been identified by determining the digestion pathway of various peptides. Insulin beta-chain (30 residues), procasomorphin (10 residues) and two peptides of five residues (proctolin and thymosin alpha 1 fragment 23-27) were utilized as model substrates. Aminopeptidase, carboxypeptidase, endopeptidase and dipeptidyl aminopeptidase activities were revealed and information on their specificity was deduced. Preliminary data on the pH-dependent activity of the peptidases were also obtained by sequence analysis of the fragment mixtures produced at different pH values.

Activation of Sulfolobus solfataricus alcohol dehydrogenase by modification of cysteine residue 38 with iodoacetic acid

Reaction of thermostable NAD(+)-dependent alcohol dehydrogenase from Sulfolobus solfataricus with iodoacetate at pH 9.0 and 37 degrees C significantly increases the oxidation rate of aliphatic and aromatic alcohols and decreases the reduction rate of aromatic aldehydes. The archaeal ADH is chemically modified and activated in a Michaelis-Menten-type reaction, where one molecule of the reagent binds per active site. NAD+ in micromolar concentration protects the enzyme against the inhibitor in an uncompetitive manner, while imidazole significantly increases the extent of the activation. Carboxymethylation selectively modifies one out of five cysteine residues per subunit, namely, Cys 38, located in the catalytic site, as determined by peptide and sequence analysis, and enhances by up to 25-fold the oxidation rate of benzyl alcohol. Carboxymethylated SsADH is less thermostable and shows a temperature optimum 30 degrees C lower than that of the native enzyme. The carboxymethylated enzyme exhibits a lower affinity toward the oxidized and reduced coenzyme. The dissociation constants for NAD+ and NADH determined at 25 degrees C and pH 8.8 are 60- and 200-fold higher, respectively, compared to the native enzyme. The significant isotope effect in alcohol oxidation suggests that hydride transfer partially limits the turnover rate of the reaction catalyzed by the modified enzyme, whereas the rate-limiting step for the native enzyme is NADH dissociation. Carboxymethylated enzyme probably gives higher maximum velocities of oxidation because of the faster dissociation of the modified enzyme-coenzyme complex.

Structural and antifungal properties of a pathogenesis-related protein from wheat kernel

We have purified and characterized a protein from the water-soluble fraction of wheat kernel (Triticum aestivum cv. S. Pastore) consisting of a single polypeptide chain blocked at its N-terminus by a pyroglutamate residue; the complete amino acid sequence has been determined by automated sequence analysis performed on peptide fragments obtained by enzymatic hydrolyses of the protein. Homology studies have shown that this protein is very similar (97% sequence identity) to the previously characterized wheatwin1 as well as to other members of the pathogenesis-related (PR) proteins of class 4; in analogy with wheatwin1, we have termed this protein wheatwin2. Both wheatwin1 and wheatwin2 have specific antifugal activity toward the wide-host-range pathogen Botrytis cinerea and the wheat-specific pathogenic fungi of wheat Fusarium culmorum and Fusarium graminearum of groups 1 and 2. On the basis of their structural and functional properties, wheatwin1 and wheatwin2 can be classified as members of the PR4 protein family; this represents the first report concerning the presence of this kind of protein in wheat.

In vitro impairment of interleukin-5 production in HLA-B8, DR3-positive individuals implications for immunoglobulin A synthesis dysfunction

Healthy subjects carrying the HLA-B8,DR3 haplotype may show a large number of immune dysfunctions. Concerning T-cell dysfunctions, the most intriguing is a defect of the early phases of T-cell activation, responsible for the impairment of in vitro mitogen-stimulated cytokine production. Regarding B-cell dysfunctions, one the most fascinating topics is the association between this haplotype and IgA deficiency in healthy blood donors. Accordingly, HLA-B8,DR3-positive healthy subjects show significantly lower values of serum IgA than HLA-B8,DR3-negative ones. Because IL-5 is a stimulating factor for the secretion of IgA by committed B cells, we have analyzed the in vitro mitogen-stimulated IL-5 production by MNCs from healthy HLA-B8,DR3-positive individuals to study whether they display an impaired production of IL-5. The results clearly demonstrate that MNCs from HLA-B8,DR3-positive individuals display significant reduction of IL-5 production, suggesting that IgA synthesis dysregulation observed in HLA-B8,DR3-positive subjects could be due to an impairment of IL-5 production.

T-cell activation in HLA-B8, DR3-positive individuals. Early antigen expression defect in vitro

The HLA-B8, DR3 haplotype is overrepresented in several autoimmune diseases, implying that genes predisposing to these disorders are linked to this haplotype. In the patients affected by these diseases, as well as in healthy HLA-B8, DR3 individuals, various dysfunctions reflecting an impairment of T-cell activation have been found. To better characterize T-cell impairment of HLA-B8, DR3-positive healthy individuals, we analyzed the surface expression of early (CD69) and late (CD71) activation phenotypes. MNC cultures were stimulated with PHA and used for T-cell phenotyping by flow cytometry analysis. The results showed that the percentage of CD69+ T cells was significantly decreased in MNC from HLA-B8, DR3+ subjects. This defect was detected in cell cultures from all subjects studied, but it attained significance only in females in the early hours after stimulation. The difference in CD69 expression between HLA-B8, DR3-positive individuals and -negative ones was not due to differences in CD4 and CD8 ratios in the HLA-B8, DR3 cells that underwent activation, as following activation the pattern of CD4 and CD8 antigen expression was the same in both groups of subjects. Concerning the late antigen CD71, no significant difference in percentage was observed between T lymphocytes from HLA-B8, DR3+ and HLA-B8, DR3- subjects at all the times studied. The analysis of the requirements for CD69 expression has suggested that sustained PKC activation and an increase of intracellular CA2+ could be responsible for TCR/CD3-mediated CD69 induction. Thus, present data suggest a defect in the signal transduction pathway of the TCR/CD3 complex.(ABSTRACT TRUNCATED AT 250 WORDS)

[Asymptomatic atrial septal aneurysm: is anticoagulant therapy always necessary? Considerations on a clinical case and evaluation of a correct cost-benefit ratio]

Atrial septal aneurysm is a cardiac abnormality with thromboembolic potential; in patients with this lesion and parameters of risk of embolic events long-term anticoagulant therapy is indicated. A clinical case of a young woman with atrial septal aneurysm and low risk parameters of cardioembolic stroke was presented.

Evaluation of body composition during low-dose estrogen oral contraceptives treatment

OBJECTIVE

To determine in a prospective study if the use of two low-dose estrogen oral contraceptives is associated with changes in weight or body composition.

DESIGN

80 outpatients referring to the family planning service, aged 18-43 years were randomly assigned to a treatment with the EE/desogestrel or EE/gestodene association, 20 patients with IUD, aged 26-40 years, were selected as a control group. Anthropometric data and body composition were taken at enrollment and after 6 and 12 months.

MAIN OUTCOME MEASURES

Anthropometric measurements included body mass index (BMI), body composition estimated by mean of Bioelectrical Impendance Analysis (BIA).

RESULTS

In the three groups weight, BMI, and total body water (TBW), and body cellular mass (BCM) remained unchanged during the study period.

CONCLUSIONS

The use of EE/desogestrel and EE/gestodene is not associated with significant variations of body weight and body composition during one year treatment.

The effect of aluminum on the vanadium-mediated oxidation of NADH

Aluminum catalyzes the oxidation of NADH by vanadate both in the presence and absence of a reducing sugar. The effect of aluminum is concentration dependent and inhibitable with superoxide dismutase but not catalase. The fructose-6-phosphate-free reaction is characterized by an initial lag phase which can be eliminated by preincubating aluminum with NADH, but is not altered by preincubating aluminum with vanadate, suggesting that the effect of aluminum is not directly on vanadate. Aluminum also catalyzes vanadyl-mediated oxidation of NADH, and this effect is similarly inhibitable by superoxide dismutase as well as catalase. It is suggested that aluminum catalyzes the oxidation of NADH by vanadium though enhancing the production of superoxide radicals and that this effect may account in part of the biological toxicity associated with aluminum, particularly when associated with the accumulation of other trace elements such as vanadium.

An algorithm to determine protein sequence alignment by utilizing data obtained from a peptide mixture and individual peptides

With the aim of limiting peptide purification steps and unambiguously ascertaining protein sequences, we have designed and implemented on a personal computer an algorithm to determine sequence alignment by utilizing data obtained from automatic Edman degradation performed on a single peptide mixture and individual peptides. The protein under study is digested by two different hydrolysis methods and fragments are just isolated from one mixture and sequenced, while the second mixture is submitted unfractionated to sequence analysis. The algorithm provides for the exact alignment of the individual peptides using the mixture data for the overlapping. We report an example of application of this approach by utilizing experimental data obtained from a protein of known sequence.

Effect of step length optimization on the aerobic demand of running

To assess whether distance runners displaying uneconomical freely chosen step lengths (FCSL) could be trained to shift FCSL toward a more optimal setting, six males and three females who exhibited uneconomical FCSL [mean optimal step length (OSL) = -9.81% of leg length from FCSL; mean change in oxygen uptake (VO2) (FCSL - OSL) = 1.46 ml.kg-1.min-1] comprised an experimental group that completed 15 treadmill sessions (30 min/day, 5 days/wk, 3 wk) of OSL training at individually determined running velocities (2.87-3.74 m/s). Training sessions featured alternating 5-min periods of combined audio and visual feedback matching OSL and no feedback. A control group of three subjects with uneconomical FCSL (2 males, 1 female) performed 3 wk of treadmill running without feedback. The extent of step length optimization was evaluated by comparing pre- and posttraining differences between FCSL and OSL and between pre- and posttraining VO2. Compared with the control group, the experimental group demonstrated a significantly (P < or = 0.05) greater relative shift in FCSL toward OSL and a marked reduction in FCSL VO2. Taken together, these results suggest that short-term audiovisual feedback training can be effective in optimizing step length and producing a decrease in aerobic demand among distance runners exhibiting uneconomical FCSL.

Molecular characterization of the functionally distinct hemoglobins of the Antarctic fish Trematomus newnesi

Antarctic fish of the family Nototheniidae usually have a single major hemoglobin (Hb 1), often a second, minor component (Hb 2, about 5% of the total), and traces of another component (Hb C, less than 1%). These are functionally similar Bohr and Root effect hemoglobins. All species of other highly endemic fish families so far investigated also have one single major hemoglobin. The hematological features of the nototheniid Trematomus newnesi are remarkably different. It is the only Antarctic species in which Hb 1 and Hb 2 display only a very weak Bohr effect and no Root effect. Perhaps consequentially, Hb C (the only component showing regulation of oxygen binding by protons and other effectors) is not present in traces but accounts for 20-25% of the total. The primary structure of the three hemoglobins of T. newnesi and of Root effect HbC present in trace amounts in another nototheniid (Pagothenia bernacchii) is discussed in relationship with oxygen binding and in terms of molecular and stereochemical models. The hemoglobin multiplicity, the oxygen binding features of Hb 1 and Hb 2, and the presence of functionally distinct components, thus reveal that the oxygen transport of T. newnesi has unique characteristics.

Hydrolysis pattern of procasomorphin by gut proteases from plant parasite Heliothis zea, determined by sequence analyses performed on the unfractionated digestion mixtures

The digestion pattern of procasomorphin, a putative precursor of beta-casomorphins (beta-casein-derived opioid peptides), by gut proteases from the plant parasite insect Heliothis zea has been determined to evaluate the possibility of introducing in plants the gene encoding for this peptide in order to confer resistance to damage by the insect. The method we used is based on the possibility of deducing the sequence of the fragments produced by proteases at different times of digestion by means of automatic Edman degradation performed on the fragment mixtures without any purification steps. This approach can be considered of general utility in studying the digestion of peptides by a mixture of proteases.

The amino acid sequence and reactive site of a single-headed trypsin inhibitor from wheat endosperm

The sequence of a trypsin inhibitor, isolated from wheat endosperm, is reported. The primary structure was obtained by automatic sequence analysis of the S-alkylated protein and of purified peptides derived from chemical cleavage by cyanogen bromide and digestion with Staphylococcus aureus V8 protease. This protein, named wheat trypsin inhibitor (WTI), which is comprised of a total of 71 amino acid residues, has 12 cysteines, all involved in disulfide bridges. The primary site of interaction (reactive site) with bovine trypsin has been identified as the dipeptide arginyl-methionyl at positions 19 and 20. WTI has a high degree of sequence identity with a number of serine proteinase inhibitors isolated from both cereal and leguminous plants. On the basis of the findings presented, this protein has been classified as a single-headed trypsin inhibitor of Bowman-Birk type.

Daily variation in step length of trained male runners

The purpose of this study was to quantify daily intra-individual variability in mean step length, a basic descriptor for the running pattern. Following 60 minutes of treadmill accommodation, nine trained male subjects (X age = 34.2 yrs +/- 7.2, X VO2max = 57.0 +/- 4.8 ml.kg-1.min-1) performed daily (Mon-Fri) 6-minute treadmill runs at three submaximal speeds (2.68, 3.13 and 3.58 m.s-1) over a 4-week period. To minimize extraneous influences, subjects refrained from road racing and completed the 20 running sessions (5 d.wk-1.4 weeks for each speed) at the same time of day and in the same footwear. Treadmill velocity was calibrated for each 6-minute running bout and step length was determined during the last 2 minutes of each run. Results indicated that mean step length and coefficient of variation values were 0.984 m and 2.50% at 2.68 m.s-1, 1.124 m and 2.22% at 3.13 m.s-1, and 1.254 m and 2.26% at 3.58 m.s-1. Reliability analyses indicated that the percentage of variation accounted for in step length across all speeds was high and improved very little as test number increased (range = 96% for two days vs 99% for five days). Taken together, these findings suggest that when testing conditions are controlled, within-subject variability in step length measures obtained at multiple submaximal running speeds is small in trained subjects and that criterion step length values can be obtained by averaging duplicate measurements.

In vitro cytokine production by HLA-B8,DR3 positive subjects

It is well known that healthy subjects carrying the HLA-B8,DR3 haplotype may show an impairment of immune system, the T cells being the most affected. To gain insight into the mechanism(s) of the impairment displayed by these subjects, efforts have been centered on the study of in vitro cytokine production because of the pivotal role played by these mediators in the activation and control of several immune functions. The available results indicate that the ability to several immune functions. The available results indicate that the ability to produce interleukin-1 (IL-1), IL-2 and the soluble form of its receptor (sIL-2R) is impaired in HLA-B8,DR3 positive healthy subjects. To better characterize the cytokine production capacity of HLA-B8,DR3 positive subjects, we have investigated the pattern of in vitro production of IL-2, sIL-2R, IL-4. IL-6 and gamma-interferon (gamma-IFN) by mononuclear cells from HLA-B8, DR3 positive subjects after phytohaemoagglutinin stimulation. A significant decrease of IL-2, sIL-2R and gamma-IFN production by HLA-B8,DR3 positive subjects was observed. No significant difference was instead found between the HLA-B8,DR3 positive subjects and the negative ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response that may observed in HLA-B8,DR3 positive subjects, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.

Natural killer and lymphokine-activated killer activity in HLA-B8,DR3-positive subjects

The haplotype HLA-B8,DR3 is over-represented in several autoimmune diseases, implying that genes predisposing people to these disorders are linked to this haplotype. In these diseases, various dysfunctions reflecting an impairment of the immune system have been found. Several reports indicate also that in HLA-B8,DR3-positive healthy subjects similar disorders may be demonstrated. In the present work, we have evaluated NK and LAK activity in these subjects. The study has been performed on monocyte-depleted peripheral blood MNCs by using, the K-562 cell line as a target for NK activity and the HL-60 cell line for as a target LAK activity. LAK cells were obtained by incubating MNCs for 3 days with 100 U/ml of rIL-2. The results of our experiments demonstrate that NK cell activity is significantly decreased in healthy subjects bearing the HLA-B8,DR3 haplotype. Since the number of circulating CD16+ cells is not significantly different between HLA-B8,DR3-positive subjects and negative ones, it is unlikely that this defect is due to a decreased number of NK cells in effector cell preparations. The observation that the treatment with rIL-2 can restore the killer activity of MNCs from these subjects suggests instead that the reduced NK activity may be due at least in part to the imbalance of cytokine network that has been demonstrated in HLA-B8,DR3-positive subjects. Finally, since a decreased NK activity has been reported in the autoimmune diseases linked to this haplotype, our results support the suggestion that immunologic changes observed in autoimmune diseases reflect systemic regulatory disorders that have a genetic basis.

[The stress test in adolescents with and without a family history of arterial hypertension: the prognostic role of a systolic arterial pressure index]

A family history of hypertension can influence the behaviour of blood pressure during ergometric stress test (EST) in normotensive subjects, so that it is also used in the assessment of risk of hypertension. To evaluate the relationship between parental history and blood pressure values during exercise, 57 consecutive adolescents (aged 10-16 years) were studied. Out of them, 25 patients have not been considered because of the presence of organic pathologies of various nature that could interfere with the pressure behaviour. All patients underwent EST with a load increase of 25 W every 3 min until the maximal age-related heart rate. The patients were divided in 2 groups based on the presence (PH+ 13 patients, mean age 13 +/- 2 years) or on the absence (PH- 19 patients, mean age 13 +/- 2 years) of parental history of hypertension. No difference in body surface and maximum workload was observed between the 2 groups. Exercise test induced an increase in systolic blood pressure (SBP) both in PH- and PH+ patients, but no significant differences were found in any stage of the exercise in the 2 groups. Maximum heart rate (HR) was not different in the 2 groups and diastolic blood pressure (DBP) was substantially unchanged during exercise. The variation of SBP (delta SBP) between maximum stress and first, third, fifth and tenth min of the recovery phase were considered. Besides, 4 SBP indexes were deduced from the ratio of SBP values at the first, third, fifth and tenth min of the recovery by the SBP value at the acme of stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetohydroxy acid synthase and threonine deaminase activities, and the biosynthesis of isoleucine-leucine-valine in Streptococcus bovis

Acetohydroxy acid synthase (AHAS) and threonine deaminase (TD) activities were found in Streptococcus bovis and shown to be involved in the biosynthesis of the branched chain amino acids isoleucine, leucine and valine. Apparent lack of repression of AHAS synthesis by the end-products and reduced sensitivity of S. bovis growth to analogues of the branched chain amino acids suggested that secretion of isoleucine, leucine and valine in the growth medium may be a consequence of the regulatory features of AHAS. A glycyl-leucine-resistant mutant with reduced TD activity secreted a reduced amount of isoleucine and an increased amount of valine, which might be a result of the reduced rate of synthesis of the isoleucine precursor alpha-ketobutyrate and of a consequent preferential carbon flow through the valine branch of the pathway.

The amino acid sequence of a protein from wheat kernel closely related to proteins involved in the mechanisms of plant defence

The amino acid sequence of wheatwin1, a monomeric protein of 125 residues isolated from wheat kernel (variety S. Pastore), is reported. Wheatwin1 is highly homologous (95%) to barwin, a protein from barley seed, which was shown to be related to the C-terminal domain of two proteins encoded by the wound-induced genes win1 and win2 in potato and to a protein encoded by the same domain of the hevein gene (hev1) in rubber tree. Similarly to barwin, wheatwin1 contains six cysteine residues all linked in disulfide bridges and the N-terminal residue is pyroglutamate. Moreover, structural studies performed on wheatwin1 and win1 protein by predictive methods demonstrated that these proteins and barwin are closely related in the secondary structure also. The high level of homology found with the product of win1, win2, and hev1 genes strongly suggests that barwin and wheatwin1 play a common role in the mechanism of plant defence.

[Effect of cilazapril therapy on diastolic filling and left ventricular hypertrophy in patients with arterial hypertension]

BACKGROUND

Of the main aspects of hypertension, left ventricular hypertrophy and appearance of cardiac dysfunction seem to be the most common and to produce an early and severe cardiac deterioration. Even in the presence of normal systolic function diastolic filling abnormalities are described. The efficacy of many antihypertensive drugs to decrease blood pressure and to reduce left ventricular hypertrophy has already been demonstrated. Cilazapril is a new ACE-inhibitor that in previous studies showed a very important antihypertensive effect. To assess its capacity, in long-term treatment, to reduce left ventricular hypertrophy we performed a prospective study on patients with mild hypertension.

MATERIAL AND METHODS

Nineteen patients (aged 48 +/- 15 years) with mild hypertension (mean arterial pressure automatically recorded for 24 hours with blood pressure ambulatorial monitoring) were treated with cilazapril (5 mg/day) for 1 year. Doppler echocardiography was performed: at the beginning, after 6 months and after one year of therapy. The following parameters were evaluated: interventricular septal and posterior wall thickness, LV end-diastolic diameter, LV mass index, early (E) and late (A) diastolic filling flow velocities and the ratio E/A.

RESULTS

A significant decrease was observed in mean arterial pressure (from 130 +/- 14 mmHg at beginning to 102 +/- 11 mmHg at six months of therapy and to 103 +/- 9 mmHg at one year of therapy). A significant reduction in LV hypertrophy and an improved diastolic filling pattern of the left ventricle was shown after six months of therapy with cilazapril; this improvement still remained after 1 year of therapy.

CONCLUSIONS

In this study antihypertensive efficacy of cilazapril has been confirmed. Moreover, in long treatment, cilazapril has been useful to reduce left ventricular hypertrophy and to improve diastolic filling without significant side effects.

HLA-B8,DR3 phenotype and the antibody response against Epstein-Barr virus

Antibodies against the viral capsid antigen (VCA) and nuclear antigens (EBNAs) of the Epstein-Barr virus (EBV) were determined in a sample of Sicilian population. A significant correlation was observed between HLA-B8,DR3 phenotype and reduced titres of antibodies to EBNAs, whereas HLA-B8,DR3 positive individuals displayed levels of antibodies to VCA comparable to those of HLA-B8,DR3 negative ones. These results further strengthen the suggestion that HLA-B8,DR3 positive subjects are low responders and that the depth of immune response depends on the fashion of antigenic challenge.

gamma-Interferon, interleukin-4 and interleukin-6 in vitro production in old subjects

It is well known that ageing is associated with various alterations of the lymphoid cell functions. Although both B and T cell are affected, the last appear to be more sensitive to ageing process. During the past years, to gain insight into thé mechanism(s) of this impairment, effort has been centered on the helper T cells specifically engaged in the production of interleukin-2 (IL-2) because of the pivotal role played by this cytokine in the activation of several immune functions. The results have demonstrated that the ability to produce IL-2 declines with age. In this paper we report the results of a study performed to determine the influence of age on the capacity to produce gamma-interferon (gamma-IFN), interleukin-4 (IL-4) and interleukin-6 (IL-6). Mononuclear cells from young and old subjects were assessed for cytokine producing capacity in response to phytohaemagglutinin stimulation. A significant decrease of gamma-IFN production by old subjects has been observed. No significant difference was instead observed between the old subjects and the young ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in elderly, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.