Biomedical subjects

M Rojas

Publications and source records attributed to M Rojas.

At least 127 records · Page 7Linked to original sources

PubMed1992

Determination of the immunization schedule for field trials with the synthetic malaria vaccine SPf 66.

The synthetic malaria vaccine SPf 66 has been shown to be safe, immunogenic and effective in trials performed with controlled groups naturally and experimentally exposed to the disease. In order to continue the trials in open populations, it was necessary to standardize the vaccination characteristics. We have performed four field trials with soldier volunteers with the aim, among others, of defining the number of doses required, the intervals between applications, the protein concentration, and the adjuvant to be used. In these trials, the vaccinated individuals' immune responses were evaluated by assaying anti-SPf 66 antibody titres, in vitro growth inhibition of the P. falciparum parasite, and the vaccinees' capacity to recognize P. falciparum native proteins. From these results we conclude that the best vaccination schedule, for adults, is three doses administered subcutaneously on days 0, 30 and 180, each containing 2 mg of the synthetic polymerized petide SPf 66 adsorbed to alum hydroxide.

Adjuvants, Immunologic↗

PubMed1992

Carcinogen metabolism in human lung tissues and the effect of tobacco smoking: results from a case--control multicenter study on lung cancer patients.

Cigarette smoking is the strongest risk factor for lung cancer, but genetically determined variations in the activities of pulmonary enzyme that metabolize tobacco-derived carcinogens may affect individual risk. To investigate whether these enzymes (e.g., CYP1A-related) can serve as markers for carcinogen-DNA damage, lung tissue specimens were taken during surgery from middle-aged men with either lung cancer or non-neoplastic lung disease. Phase I [aryl hydrocarbon hydroxylase (AHH), ethoxycoumarin O-deethylase (ECOD)] and phase II (epoxide hydrolase, UDP-glucuronosyltransferase, glutathione S-transferase) enzyme activities, glutathione and malondialdehyde contents were determined in lung parenchyma and/or bronchial tissues; some samples were also analyzed for DNA adducts, using 32P-postlabeling. The data were then analyzed for the following: a) differences in metabolic profiles between bronchial and parenchymal lung tissue; b) the effect of recent exposure to tobacco smoke on enzyme inducibility and benzo[a]pyrene metabolism; c) differences in enzyme inducibility between lung cancer and non-lung cancer patients; d) the effect of smoking on metabolism of mutagens in vitro; e) pulmonary DNA adduct levels and AHH activity in lung parenchyma of smokers and ex-smokers; f) lipid peroxidation products in lung tissue from lung cancer and non-lung cancer patients, as related to smoking habits and degree of airway obstruction; and g) prognostic value of AHH pulmonary activity in lung cancer patients. The results demonstrate a pronounced effect of tobacco smoke on pulmonary metabolism of xenobiotics and prooxidant state and suggest the existence of a metabolic phenotype at higher risk for tobacco-associated lung cancer.

7-Alkoxycoumarin O-Dealkylase↗

PubMed1992

Development of a program of behavior modification directed to the rehabilitation of drug-dependent patients: treatment and follow-up of 223 cases.

The study reports treatment and follow-up of compulsive drug-consuming patients (mainly of coca paste). The program used was based on a behavioral cognitive and instructional model. The traditional functional analysis was modified to include the therapeutical work in seven behavioral areas: (1) drug use; (2) behavior during free time; (3) behavior at work; (4) social behavior; (5) self- and environmental management behaviors; (6) problem solving and decision-making behaviors; (7) recognition, evaluation, and modification of irrational beliefs. For each area objectives, therapeutical procedures, control and evaluation methods, and termination criteria were determined. Patients engaged in a multiple activity program and received individual and group therapy. Out of 223 male patients, 130 were discharged (that is, they fulfilled all the conditions stated by the program) and 93 patients abandoned treatment. For evaluation purposes a test was used to determine the accomplishment of the behavioral objectives. Follow-up interviews after 6 to 72 months showed that although 24 patients relapsed to drug use, 106 (81.48%) of the patients who had finished the program restrained from using drugs and obtained high scores in all seven behavioral areas.

Adolescent↗

PubMed1992

Parasitic oligosaccharide residues recognized by patients with mucocutaneous and localized cutaneous leishmaniasis.

Humoral immune responses were studied in 118 Venezuelan patients with either active mucocutaneous (MCL) or localized cutaneous leishmaniasis (LCL). Most patients had elevated antibody levels to the six promastigote oligosaccharide residues studied: galactosyl(alpha 1-2)galactose, galactosyl(alpha 1-3)galactose, galactosyl(alpha 1-6)galactose, galactosyl(alpha 1-3)mannose, galactofuranosyl(beta 1-3)mannose, and galactocerebroside. Significantly higher antibody levels were found in patients with MCL against galactosyl(alpha 1-3)galactose and Leishmania tropica glycoinositol phospholipid (GIPL)-1, GIPL-2, and GIPL-3 compared with patients with LCL. For both clinical forms of American cutaneous leishmaniasis (ACL), the most reactive antigen was galactosyl(alpha 1-3)galactose, with elevated levels found in 63% and 79% of MCL and LCL patients, respectively. In patients with MCL and LCL, no significant relationship was found between antibody levels against a given oligosaccharide residue and clinical parameters such as age, leishmanin diameter, number of skin lesions, or time of evolution. It is noteworthy that 33% and 15% of MCL and LCL patients, respectively, did not have elevated antibody levels against the six different oligosaccharide residues studied. This suggests the presence of a subpopulation of non-humoral immunoreactive ACL patients. The relationship between abnormal levels of oligosaccharide antibodies and the final outcome of the disease remains to be established.

Adult↗

PubMed1992

Characterization of a natural human antibody with anti-galactosyl(alpha 1-2)galactose specificity that is present at high titers in chronic Trypanosoma cruzi infection.

An antibody reactive with the galactosyl(alpha 1-2)galactose [gal(alpha 1-2)gal] epitope was characterized in human sera by enzyme-linked immunosorbent assay, red blood cell (RBC) and laminin absorption, and oligosaccharide inhibition. This antibody was found evenly distributed between the IgG and IgM classes and was present at high titers in the serum of all normal adults studied, but in 75% of children less than three years of age, it was observed at the lower limit of detection, and gradually increased to adult levels by the age of six. Although this antibody bound to gal(alpha 1-3)gal-linked synthetic antigens, it did not bind to the same residues present in rabbit, rat, and guinea pig RBC or in murine laminin or nidogen. These latter results, plus the fact that antigen-antibody binding was strongly blocked by gal(alpha 1-2)gal but not by methyl-alpha-galactopyranoside or melibiose, suggest that this antibody is indeed different from anti-gal(alpha 1-3)gal antibody. Anti-gal(alpha 1-2)gal antibody levels were significantly elevated in 66% of patients with chronic chagasic cardiomyopathy, but were not elevated in patients with different clinical forms of leishmaniasis, Trypanosoma rangeli-infected patients, or in patients with 15 other infectious and inflammatory diseases. Gal(alpha 1-2)gal antibodies did not absorb to intact T. cruzi parasites, but absorbed strongly to trypomastigote and epimastigote sonicates, suggesting some masking of reactive epitopes.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗

PubMed1991

A mouse carcinoembryonic antigen gene family member is a calcium-dependent cell adhesion molecule.

Carcinoembryonic antigen (CEA) is a heavily glycosylated protein used clinically as a tumor marker to detect recurrences of many types of tumors. This glycoprotein belongs to the immunoglobulin superfamily and is the prototype of the large CEA family of proteins. In a concerted effort to determine the function(s) of this family, we have been investigating a similar family of proteins in the mouse. In this paper, we report the characterization of a new mouse family member named mmCGM2; this gene product is highly homologous to the human biliary glycoprotein of the CEA gene family and to a rat hepatocyte ecto-ATPase. In vitro transcription, translation, and glycosylation experiments have revealed that the mmCGM2 cDNA encodes a glycoprotein of 42 kDA with a putative extracellular N-terminal domain and a C2-set type immunoglobulin domain. We have used this cDNA as a probe to detect many different transcripts (1.5-4.6 kilobases) in mouse adult tissues, some of which are specific to particular tissues, while others are expressed ubiquitously. After transfection of a plasmid bearing the mmCGM2 cDNA into mouse fibroblasts known to lack CEA-related gene expression, transfectant cell clones were chosen and used to investigate the adhesion properties conferred onto the cells. Cells expressing the mmCGM2 cDNA in a sense orientation aggregated in a calcium- and temperature-dependent fashion. Together with human biliary glycoprotein, the mmCGM2 gene product is the first member of the immunoglobulin superfamily to exhibit calcium-dependent adhesion. The constant tissue reorganization necessary to the differentiation of precise structures in tissues which express these gene family members (colon, liver, and uterus) implies the necessity of a variety of specific cell-cell contacts which could utilize the cell adhesion properties that we have demonstrated.

Amino Acid Sequence↗

PubMed1991

Lectin histochemistry in mucinous and serous ovarian neoplasms.

The lectin-binding properties of 44 cases of serous and mucinous ovarian cystadenoma, tumor of low malignant potential (LMP), and invasive carcinoma were examined histochemically. Wheat germ agglutinin (WGA), concanavalin A (con A), Ulex europaeus agglutinin I (UEA-I), peanut agglutinin (PNA), Ricinus communis agglutinin I (RCA-I), soybean agglutinin (SBA), and Robina pseudoaccacia (RPA) were employed. All the lectins examined were bound to neoplastic epithelial cells of benign and malignant tumors, but none bound exclusively to ovarian tumor cells. Different lectin-binding patterns between serous and mucinous neoplasms were observed, with the exception of RPA. UEA-I, con A, RPA, and PNA in serous neoplasms and UEA-I, RPA, and WGA in mucinous neoplasms demonstrated lectin-binding properties of LMP tumors intermediate between those of cystadenoma and invasive carcinoma. These findings indicate that serous and mucinous ovarian neoplasms contain different glycoconjugates, that malignant transformation of the neoplasms is associated with alteration of these glycoconjugates, and especially that LMP tumors have a different composition of cellular glycoconjugates from that of invasive ovarian carcinoma.

Adenocarcinoma, Mucinous↗

PubMed1991

Studies on the humoral immune response to a synthetic vaccine against Plasmodium falciparum malaria.

A synthetic vaccine against the asexual blood stages of P. falciparum, the SPf 66 synthetic hybrid polymer, composed of peptides derived from three merozoite membrane proteins as well as one peptide from the sporozoite CS protein, has been developed by our group and tested in different protection assays in Aotus monkeys as well as in human volunteers. This study evaluates the humoral immune response induced by the SPf 66 protein vaccination in adult human volunteers from the Colombian Pacific coast as follows: determination of specific IgG antibody levels against SPf 66 by FAST-ELISA after each immunization; analysis of antibody reactivity with P. falciparum schizont lysates by immunoblots; and determination of the in vitro parasite growth inhibition. A clear boosting effect, dependent on time and dose, was observed in the antibody production kinetics. These antibodies also specifically recognize three proteins of the P. falciparum schizont lysate corresponding to the molecular weights of the proteins from which the amino acid sequence was derived. These sera were also capable of markedly inhibiting in vitro parasite growth.

Adolescent↗

PubMed1991

Genetic control of the immune response to a synthetic vaccine against Plasmodium falciparum.

Two independent vaccination trials using a hybrid synthetic polypeptide containing epitopes from four proteins of Plasmodium falciparum were performed. In the first trial 63 and in the second 122 volunteers were vaccinated, using different immunization schedules. The analysis of the humoral response to the vaccine, measured by IgG antibody titres to the polypeptide showed a bimodal distribution in both cases suggesting genetic control of the immune response to this protein. There was a small group of low or non-responders and a large group of good responders. HLA phenotyping of the two groups disclosed an association of the low responders to HLA-DR4 antigens with chi-square P value of 0.00039 when compared with the good responders group. These findings provide evidence for the genetic control of the immune response to the synthetic vaccine by the association of this response with particular alleles of the HLA class II antigens; such findings may lead to an explanation of the mechanism involved in disease susceptibility and need to be used in the design of a totally effective vaccine.

Adolescent↗

PubMed1991

Glycoinositol phospholipids from American Leishmania and Trypanosoma spp: partial characterization of the glycan cores and the human humoral immune response to them.

The glycoinositol phospholipid (GIPL) profiles of American Leishmania spp. (L. mexicana and L. braziliensis), Leishmania donovani, and American Trypanosoma spp. (T. cruzi and T. rangeli) were compared. The major GIPLs in these parasites include tetraglycosyl-, pentaglycosyl-, and hexaglycosylphosphatidylinositol. These were partially identified by their comigration by high-performance thin-layer chromatography with purified L. major GIPLs, gas-liquid chromatography of the monosaccharides released after aqueous HF treatment, N-acetylation and methanolysis, sensitivity to exoglycosidases, and antibody absorption on several specific natural haptens. Members of the genus Leishmania have two other highly polar glycolipids, while the T. rangeli glycolipid profile was quite different from those of other kinetoplastids that were studied. On a weight basis, the glycan core of L. major GIPL-1 is the most reactive, followed by GIPL-3 and GIPL-2. Antibodies to the core glycans of GIPL-1, GIPL-2, and GIPL-3 were present at a low titer in the serum of every normal individual studied, while elevated GIPL-2 antibody levels were present in 80 to 100% of T. cruzi-, T. rangeli-, or L. donovani-infected patients, with lower values being found for GIPL-3 (30 to 60%) and GIPL-1 (30 to 50%). Except for GIPL-2 antibodies, which were mainly located on immunoglobulin G (IgG) and IgM, GIPL-1 and GIPL-3 antibodies were mainly distributed in IgM, with lower reactivity present in IgG. Antigen-antibody binding was very selectively blocked with Gal(alpha 1-3)Man, or Gal(beta 1-4)Man, Gal(alpha 1-3)Gal, and Gal(alpha 1-6)Gal for GIPL-1, GIPL-2, and GIPL-3 antibodies, respectively.

Animals↗

PubMed1990

Adolescent suicide attempters. Response to suicide-prevention programs.

As part of a controlled evaluation of three suicide-prevention curricula delivered to 1438 ninth- and 10th-grade students, 63 adolescents were identified as having made a suicide attempt. Their attitudes about suicide and help seeking were compared with those of 910 nonattempters drawn from the same population. Reaction to the prevention program was assessed by comparing the responses of the 35 attempters exposed to the programs with responses of 524 exposed nonattempters. The impact of the programs was assessed by comparing 35 exposed attempters with 28 attempters from a control group. Self-identified attempters were less likely to endorse views consistent with the curricula at baseline, but there was little evidence that the programs were successful in influencing these views. There was some evidence that previous attempters were more upset by the programs than their nonattempter peers. The prevalence of suicide attempts as defined in this study by self-report was higher than that reported in studies using interview techniques.

Adolescent↗

PubMed1990

Inhibitory effect of a toxic peptide isolated from a waterbloom of Microcystis sp. (Cyanobacteria) on iron uptake by rabbit reticulocytes.

The effect of a soluble toxin purified from the algae bloom of a eutrophic lake dominated by Microcystis on the receptor-mediated endocytosis of ferro-transferrin in rabbit reticulocytes was studied. The toxin was a very effective inhibitor of cell iron uptake. Kinetic studies using 125I, 59Fe-labeled transferrin indicated that the step of ferrotransferrin internalization was selectively inhibited by the toxin while the surface receptor-binding capacity, the externalization of previously internalized transferrin, and the cellular ATP levels were not affected. These findings indicate that the reduction of iron uptake caused by the toxin is due to inhibition of the internalization of surface-located transferrin-transferrin receptor complexes, perhaps due to a disruption of cytoskeleton integrity.

Animals↗

PubMed1990

A new sensitive fluorometric assay for the metabolism of (--)-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene by human hair follicles.

A new sensitive fluorometric assay was established to measure the stereospecific formation of benzo[alpha]pyrene tetrols formed after cytochrome P450-dependent metabolism of (--)-7,8-dihydroxy-7,8- dihydrobenzo[a]pyrene by human hair follicles. This simple assay requires three human hair follicles and a low (0.5-2.0 microM) substrate concentration and has a limit of detection of approximately 0.3 fmol of tetrols. Freshly isolated human hair follicles from 20 adult volunteers (10 non-smokers and 10 smokers) were assayed. While intersubject and seasonal variations were observed, the assay was found to be reproducible for a given subject. This rapid and non-invasive assay provides a new means for metabolic phenotyping of human subjects for their capacity to metabolize (--)-7,8-dihydroxy-7,8-dihydrobenzo[alpha]pyrene to its carcinogenic form (+)anti-benzo[a]pyrene diolepoxide.

Adult↗

PubMed1990

MSN-1 antibody in the evaluation of female genital tract adenocarcinomas.

The reactivity of a new monoclonal antibody (MAb), MSN-1, raised against a human endometrial cancer cell line (SNG-II), was studied in a variety of endometrial, endocervical, and ovarian carcinomas as well as normal cycling endometrium. Moderate to strong reactivity (2-3+) was seen in six of nine normal secretory endometria (67%), one of 10 normal proliferative endometria (10%), 18 of 18 endometrial adenocarcinomas (100%), 10 of 11 endometrioid ovarian adenocarcinomas (91%), seven of nine clear cell ovarian adenocarcinomas (78%), one of 12 endometrial hyperplasias without atypia (9%), two of four endometrial hyperplasias with atypia (50%), zero of five endometrial serous adenocarcinomas, two of 17 serous ovarian adenocarcinomas (12%), zero of 10 intestinal-type mucinous ovarian adenocarcinomas, and zero of nine metastatic adenocarcinomas in ovary. Endocervical adenocarcinomas showed moderate to strong staining in 75% (six of eight). It is concluded that MSN-1 can be used to confirm endometrioid/clear cell differentiation in ovarian and endometrial tumors, cannot be used to discriminate endocervical from endometrial differentiation, cannot be used to discriminate atypical hyperplasia from carcinoma, and may be useful to distinguish between atypical (premalignant) endometrial hyperplasias and those without atypia.

Adenocarcinoma↗

PubMed1990

A galactosyl(alpha 1-3)mannose epitope on phospholipids of Leishmania mexicana and L. braziliensis is recognized by trypanosomatid-infected human sera.

An immunoglobulin M antibody reactive with galactosyl(alpha 1-3)mannose [Gal(alpha 1-3)Man] residues present on phospholipids extracted from Leishmania mexicana and L. braziliensis was found to be present in high titer in the serum of every normal individual studied. Periodate oxidation, acid hydrolysis, or acetylation suppressed immunoreactivity, suggesting that an oligosaccharide chain was responsible for antibody binding. Interaction occurs only with alpha-Gal terminal residues, since treatment of purified glycophospholipids with alpha-galactosidase but not with beta-galactosidase abolished it. Antibody bound to galactosyl(alpha 1-3)galactose-linked synthetic antigens but did not bind to the same residues present in rabbit, rat, and guinea pig erythrocytes or in murine laminin. Antigen-antibody binding was strongly blocked with Gal(alpha 1-3)Man and Gal(beta 1-4)Man. These results plus inhibition studies with several oligosaccharides suggest that they are indeed different from antibodies against the galactosyl(alpha 1-3)galactose residue. Anti-Gal(alpha 1-3)Man antibody values were significantly elevated in 89% of patients with diffuse cutaneous leishmaniasis, 84% of patients with localized cutaneous leishmaniasis, 69% of patients with mucocutaneous leishmaniasis, and 44 and 62% of patients with Trypanosoma cruzi or T. rangeli infection, respectively, but not in patients with 15 other different infectious and inflammatory diseases. Anti-Gal(alpha 1-3)Man antibody readily absorbed to American Leishmania and Trypanosoma culture forms, suggesting a surface membrane localization of reactive epitope. Gal(alpha 1-3)Man-bearing glycophospholipid was easily extracted from American Leishmania promastigotes and T. cruzi trypomastigotes as well as from American Trypanosoma culture forms. The possibility that this antibody arises against parasitic glycophospholipid-linked Gal(alpha 1-3)Man terminal residues is proposed.

Animals↗

PubMed1990

Elevated cerebroside antibody levels in human visceral and cutaneous leishmaniasis, Trypanosoma rangeli infection, and chronic Chagas' disease.

A natural cerebroside (antiC) IgM antibody was found at relatively high levels in the serum of every healthy individual studied. The reactivity of the antibody was assessed by using highly purified bovine brain galactocerebroside (galC) or human glucocerebroside (gluC) as antigen. The importance of fatty acid moiety of galC in antigen-antibody reaction was demonstrated by low immunoreactivity using 1-beta-D-galactosyl sphingosine (GS) as antigen and by the absence of absorption to GS-bearing liposomes. The presence of alpha-hydroxy and non-hydroxy fatty acids in galC did not modify its immunoreactivity. Cerebroside antibody binding activity was only partially blocked by 0.5 M galactose or alpha- and beta-methylgalactopyranoside, suggesting poor specificity of antiC for a specific glycosidic residue or linkage. In fact, liposome-bearing gluC absorbed galC. AntiC did not adsorb on rabbit, guinea pig, or human erythrocytes (RBC), but absorbed strongly on rat RBC. Elevated antibody levels were found in 57% of Kala azar patients, 56% of Trypanosoma rangeli-infected patients, 30% of chronic chagasic patients, and 20% of cutaneous leishmaniasis patients, but were not found in 16 other inflammatory or infectious diseases studied. This suggests an association between Kinetoplastida infection and elevated levels of antiC, with parasitic galC acting probably as a highly immunogenic antigen. A possible role of anti-galC in the neuropathological symptoms of Chagas' disease and in the control of parasitemia levels in T. rangeli-infected individuals is discussed.

Animals↗

PubMed1990

Biliary glycoprotein, a member of the immunoglobulin supergene family, functions in vitro as a Ca2(+)-dependent intercellular adhesion molecule.

Intercellular adhesion molecules can be classified as Ca2+ dependent or Ca2+ independent. This classification has significant functional implications regarding cellular interactions. The best characterized Ca2(+)-dependent adhesion molecules, such as L-CAM or E-cadherin, belong to the family of closely related cell surface molecules called cadherins. On the other hand, those immunoglobulin supergene family members which function as adhesion molecules, such as neural cell adhesion molecule, have been found to be Ca2+ independent. In agreement with this generalization, we have recently shown that carcinoembryonic antigen (CEA) and nonspecific cross-reacting antigen (NCA), two closely related members of the CEA family, a subset of the immunoglobulin supergene family, function in vitro as Ca2(+)-independent adhesion molecules. In contrast, we show here that transfectants of a third member of the CEA family, biliary glycoprotein (BGP), also aggregate homotypically in suspension but require Ca2+ for aggregation. In addition, like the cadherins and unlike CEA or NCA or other adhesion molecules of the immunoglobulin supergene family, BGP transfectant aggregation requires physiological temperatures. Two forms of BGP, with three and two immunoglobulin C2-set domains, show Ca2(+)- and temperature-dependent adhesion, so that these properties do not reside in the third C2-set domain. The significance of this expression in the range of functional properties of the immunoglobulin supergene family and its CEA subset is discussed.

Antigens, CD↗

PubMed1989

Immunogenic Gal alpha 1----3Gal carbohydrate epitopes are present on pathogenic American Trypanosoma and Leishmania.

Anti-Gal is a natural antibody present in unusually high concentrations in human sera. It constitutes as much as 1% of circulating IgG and displays a distinct specificity for the Gal alpha 1----3Gal carbohydrate epitope. In the present study, we have found in the sera of patients with Chagas' disease and Leishmania infection anti-Gal titers 10- and 16-fold higher than that of healthy or bacteria-infected individuals. This increase in anti-Gal titer seemed to be the result of a specific immune response toward parasitic Gal alpha 1----3Gal epitopes. Binding studies of affinity chromatography-purified anti-Gal antibodies to Trypanosoma cruzi and American Leishmania parasites indeed demonstrated the presence of Gal alpha 1----3Gal epitopes on these parasites. This finding was supported by the observed binding to the parasites of two additional Gal alpha 1----3Gal recognizing molecules: the mAb Gal-13, and the lectin, Bandeiraea simplicifolia I B4. Furthermore, the binding of both anti-Gal antibody and of the B. simplicifolia I B4 lectin could be inhibited by galactose, and not glucose. In addition, removal of the terminal alpha-galactosyl residues from the parasites by pretreatment with alpha-galactosidase, or the oxidation of the binding epitopes by periodate prevented the subsequent binding of both the antibody and the lectin. A crude leishmanial lipid extract readily bound these three reagents, suggesting that at least part of these epitopes are of a glycolipid nature. These Gal alpha 1----3Gal epitopes may thus serve as an antigenic source for the excess production of anti-Gal. In view of the naturally high level of anti-Gal in humans and its binding to T. cruzi and Leishmania, it is argued that these antibodies may contribute to the natural defense against the invasion of such parasites.

Animals↗