Land abandonment as driver of woody vegetation dynamics in Tamaulipan thornscrub at Northeastern Mexico.

Background: Vegetation structure is defined as the temporal and spatial distribution of plant species in a particular site. Vegetation structure includes vertical and horizontal distribution and has been widely used as an indicator of successional changes. Ecological succession plays an essential role in the determination of the mechanisms that structure plant communities under anthropogenic disturbances. After an anthropogenic disturbance, such as grazing, forests follow changes in the original composition and vegetation structure, which eventually could restore some of their attributes to become mature forests again. To know how the time of abandonment affects woody plant communities, we ask the following questions: (1) How does the species richness, diversity, and vertical structure (A index) change concerning the time of abandonment? (2) Are species similarities among woody vegetation communities determined by land abandonment? (3) Which woody species have the highest ecological importance in each successional stage? Methods: We explored how successional stages after land abandonment mediated the species richness, species diversity (alpha and beta), and ecological importance value index on four areas of Tamaulipan thornscrub. We selected four areas that differed in time of abandonment: 10, 20, 30, and >30 years. The first three areas were used for cattle grazing, whereas the >30-year area was selected as a control since it does not have a record of disturbance by cattle grazing or agriculture. During the summer of 2012, we randomly established four square plots (40 m × 40 m) in each area, separated at least 200 m from each other. In each plot, we recorded all woody individuals per species with a basal diameter ≥1 cm at 10 cm above ground level. We estimated species richness indices, species diversity (alpha and beta), and ecological importance value index. Results: We recorded 27 woody species belonging to 23 genera and 15 families. Fabaceae accounted for 40% of the species. Acacia farnesiana was the most important and abundant species in the first three successional stages. We suggested that older successional stages of Tamaulipan thornscrub promote woody plant communities, characterized by a higher complex structure than younger communities. We observed the highest species similarity between the sites with a closer time of abandonment, while the lowest similarity was shown between the sites with extreme time of abandonment. We conclude that Tamaulipan thornscrub shows a similar trend of ecological succession to other dry forests and the time of abandonment has a high mediation on plant dynamics in the Tamaulipan thornscrub. Also, we stand out the importance of secondary forests for Tamaulipan thornscrub woody plant communities. Finally, we recommended future studies include aspects of regeneration speed, the proximity of mature vegetation, and the interactions of plants with their seed dispersers.

Relative contribution of ecological and biological attributes in the fine-grain structure of ant-plant networks.

BACKGROUND: Ecological communities of interacting species analyzed as complex networks have shown that species dependence on their counterparts is more complex than expected at random. As for other potentially mutualistic interactions, ant-plant networks mediated by extrafloral nectar show a nested (asymmetric) structure with a core of generalist species dominating the interaction pattern. Proposed factors structuring ecological networks include encounter probability (e.g., species abundances and habitat heterogeneity), behavior, phylogeny, and body size. While the importance of underlying factors that influence the structure of ant-plant networks have been separately explored, the simultaneous contribution of several biological and ecological attributes inherent to the species, guild or habitat level has not been addressed. METHODS: For a tropical seasonal site we recorded (in 48 censuses) the frequency of pairwise ant-plant interactions mediated by extrafloral nectaries (EFN) on different habitats and studied the resultant network structure. We addressed for the first time the role of mechanistic versus neutral determinants at the 'fine-grain' structure (pairwise interactions) of ant-plant networks. We explore the simultaneous contribution of several attributes of plant and ant species (i.e., EFN abundance and distribution, ant head length, behavioral dominance and invasive status), and habitat attributes (i.e., vegetation structure) in prevailing interactions as well as in overall network topology (community). RESULTS: Our studied network was highly-nested and non-modular, with core species having high species strengths (higher strength values for ants than plants) and low specialization. Plants had higher dependences on ants than vice versa. We found that habitat heterogeneity in vegetation structure (open vs. shaded habitats) was the main factor explaining network and fine-grain structure, with no evidence of neutral (abundance) effects. DISCUSSION: Core ant species are relevant to most plants species at the network showing adaptations to nectar consumption and deterrent behavior. Thus larger ants interact with more plant species which, together with higher dependence of plants on ants, suggests potential biotic defense at a community scale. In our study site, heterogeneity in the ant-plant interactions among habitats is so prevalent that it emerges at community-level structural properties. High frequency of morphologically diverse and temporarily-active EFNs in all habitats suggests the relevance and seasonality of plant biotic defense provided by ants. The robust survey of ecological interactions and their biological/ecological correlates that we addressed provides insight of the interplay between adaptive-value traits and neutral effects in ecological networks.

Flower-mediated plant-butterfly interactions in an heterogeneous tropical coastal ecosystem.

BACKGROUND: Interspecific interactions play an important role in determining species richness and persistence in a given locality. However at some sites, the studies, especially for interaction networks on adult butterflies are scarce. The present study aimed the following objectives: (1) determine butterfly species richness and diversity that visit flowering plants, (2) compare species richness and diversity in butterfly-plant interactions among six different vegetation types and (3) analyze the structure of butterfly-flowering plant interaction networks mediated by flowers. METHODS: The study was developed in six vegetation types within the natural reserve of La Mancha, located in Veracruz, Mexico. In each vegetation type, we recorded the frequency of flower visits by butterflies monthly in round plots (of radius 5 m) for 12 months. We calculated Shannon diversity for butterfly species and diversity of interactions per vegetation type. We determined the classic Jaccard similarity index among vegetation types and estimated parameters at network and species-level. RESULTS: We found 123 species of butterflies belonging to 11 families and 87 genera. The highest number of species belonged to Hesperiidae (46 species), followed by Nymphalidae (28) and Pieridae (14). The highest butterfly diversity and interaction diversity was observed in pioneer dune vegetation (PDV), coastal dune scrub (CDS) and tropical deciduous flooding forest and wetland (TDF-W). The same order of vegetation types was found for interaction diversity. Highest species similarity was found between PDV-CDS and PDV-TDF. The butterfly-plant interaction network showed a nested structure with one module. The species Ascia monuste, Euptoieta hegesia and Leptotes cassius were the most generalist in the network, while Horama oedippus, E. hegesia, and L. cassius were the species with highest dependencies per plant species. DISCUSSION: Our study is important because it constitutes a pioneer study of butterfly-plant interactions in this protected area, at least for adult butterflies; it shows the diversity of interactions among flowering plants and butterflies. Our research constitutes the first approach (at a community level) to explore the functional role of pollination services that butterflies provide to plant communities. We highlighted that open areas show a higher diversity and these areas shared a higher number of species that shaded sites. In the interaction networks parameters, our results highlighted the higher dependence of butterflies by the flowers on which they feed than vice versa. In conclusion, the plant species (as a feeding resource) seem to limit the presence of butterfly species. Thus, this protected area is highly relevant for Lepidoptera diversity and the interaction between these insects and flowering plants. We suggest that studying plant and butterfly diversity in tropical habitats will provide insight into their interspecific interactions and community structure.

Epidemiological characteristics of patients with pelvic tumors submitted to surgical treatment / Características epidemiológicas dos pacientes com tumores pélvicos submetidos a tratamento cirúrgico

ABSTRACT Objective: Describe the epidemiological profile of patients with primary or secondary neoplastic lesions in the pelvis who required a surgical procedure such as hemipelvectomy. Methods: This study retrospectively evaluated 69 patients located in the database of a São Paulo educational institution, subject to surgical hemipelvectomy treatment between January 1990 and December 2013. All patients had previous diagnosis of bone tumor (primary or metastatic) in the pelvis (ilium, ischium, pubis, and/or sacrum). Results: Analyzing the data obtained in this study, it was observed that these are partly similar to those found in the literature, with primary bone malignancies as the main diagnosis; general injuries affecting the pelvic area I (pelvic bone) and its most frequent complication, infection. The differences are mainly due to rarity of the bone tumors evaluated in this study, and the type of surgical procedure in question, which is even more unusual. Conclusion: Building a picture that conveys the reality of each diagnosis and that indicates which characteristics of these patients would better resemble an absolute or relative indication for the realization of hemipelvectomy is harder by the rarity of these cases.

RESUMO Objetivo: Traçar o perfil epidemiológico dos pacientes com lesões neoplásicas na pelve, primárias ou secundárias, para as quais foi necessário procedimento cirúrgico do tipo hemipelvectomia. Métodos: Foram avaliados, retrospectivamente, 69 pacientes localizados no banco de dados de uma instituição de ensino de São Paulo, submetidos a tratamento cirúrgico tipo hemipelvectomia entre janeiro de 1990 e dezembro de 2013. Todos os pacientes apresentavam diagnóstico prévio de tumor ósseo (primário ou metastático) na pelve (ílio, ísquio, púbis e/ou sacro). Resultados: Ao analisar os dados obtidos no presente estudo, observou-se que esses são em parte semelhantes aos encontrados na literatura mundial, apresentam como principal diagnóstico as neoplasias malignas ósseas primárias. Em geral, as lesões acometeram a zona I pélvica (osso ilíaco) e a complicação mais frequentemente observada foi a infecção. As diferenças encontradas são devidas principalmente à raridade dos tumores ósseos avaliados nesses estudos e ao tipo de procedimento cirúrgico em questão, esses ainda mais incomuns. Conclusão: Construir um panorama que transmita a realidade de cada diagnóstico e indique quais as características que esses pacientes apresentam que mais se aproximariam como indicações relativas ou absolutas para o procedimento de hemipelvectomia encontra na raridade desses casos o seu maior obstáculo.

Epidemiological characteristics of patients with pelvic tumors submitted to surgical treatment.

OBJECTIVE: Describe the epidemiological profile of patients with primary or secondary neoplastic lesions in the pelvis who required a surgical procedure such as hemipelvectomy. METHODS: This study retrospectively evaluated 69 patients located in the database of a São Paulo educational institution, subject to surgical hemipelvectomy treatment between January 1990 and December 2013. All patients had previous diagnosis of bone tumor (primary or metastatic) in the pelvis (ilium, ischium, pubis, and/or sacrum). RESULTS: Analyzing the data obtained in this study, it was observed that these are partly similar to those found in the literature, with primary bone malignancies as the main diagnosis; general injuries affecting the pelvic area I (pelvic bone) and its most frequent complication, infection. The differences are mainly due to rarity of the bone tumors evaluated in this study, and the type of surgical procedure in question, which is even more unusual. CONCLUSION: Building a picture that conveys the reality of each diagnosis and that indicates which characteristics of these patients would better resemble an absolute or relative indication for the realization of hemipelvectomy is harder by the rarity of these cases.

OBJETIVO: Traçar o perfil epidemiológico dos pacientes com lesões neoplásicas na pelve, primárias ou secundárias, para as quais foi necessário procedimento cirúrgico do tipo hemipelvectomia. MÉTODOS: Foram avaliados, retrospectivamente, 69 pacientes localizados no banco de dados de uma instituição de ensino de São Paulo, submetidos a tratamento cirúrgico tipo hemipelvectomia entre janeiro de 1990 e dezembro de 2013. Todos os pacientes apresentavam diagnóstico prévio de tumor ósseo (primário ou metastático) na pelve (ílio, ísquio, púbis e/ou sacro). RESULTADOS: Ao analisar os dados obtidos no presente estudo, observou-se que esses são em parte semelhantes aos encontrados na literatura mundial, apresentam como principal diagnóstico as neoplasias malignas ósseas primárias. Em geral, as lesões acometeram a zona I pélvica (osso ilíaco) e a complicação mais frequentemente observada foi a infecção. As diferenças encontradas são devidas principalmente à raridade dos tumores ósseos avaliados nesses estudos e ao tipo de procedimento cirúrgico em questão, esses ainda mais incomuns. CONCLUSÃO: Construir um panorama que transmita a realidade de cada diagnóstico e indique quais as características que esses pacientes apresentam que mais se aproximariam como indicações relativas ou absolutas para o procedimento de hemipelvectomia encontra na raridade desses casos o seu maior obstáculo.

Flower, fruit phenology and flower traits in Cordia boissieri (Boraginaceae) from northeastern Mexico.

We characterized variations in Cordia boissieri flowers and established if these variations occur between plants or between flowering events. Flowering and fruiting was measured for 256 plants. A GLM test was used to determine the relationship between flowering and fruit set processes and rainfall. We performed measurements of floral traits to detect variations within the population and between flowering events. The position of the anthers with respect to the ovary was determined in 1,500 flowers. Three out of four flowering events of >80% C. boissieri plants occurred after rainfall events. Only one flowering event occurred in a drought. Most plants flowered at least twice a year. The overlapping of flowering and fruiting only occurred after rainfall. Anthesis lasted three-to-five days, and there were two flower morphs. Half of the plants had longistylus and half had brevistylus flowers. Anacahuita flower in our study had 1-4 styles; 2-9 stamens; 6.5-41.5 mm long corolla; sepals from 4.5-29.5 mm in length; a total length from 15.5-59 mm; a corolla diameter from 10.5-77 mm. The nectar guide had a diameter from 5-30.5 mm; 4-9 lobes; and 5 distinguishable nectar guide colors. The highest variation of phenotypic expression was observed between plants.

Atrophy, focal spinal cord lesions and alterations of diffusion tensor imaging (DTI) parameters in asymptomatic virus carriers and patients suffering from human T-lymphotrophic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP).

In tropical spastic paraparesis, spinal cord atrophy is a well-known finding in magnetic resonance imaging. But in contrast to histological reports, focal lesions of the spinal cord have only been described in imaging reports in exceptional acute cases. Here, we looked for such focal lesions and for alterations of diffusion tensor imaging parameters of the long fibre tracts in the usual case of a long-standing and slowly progressive disease. We examined 10 symptomatic patients, 11 seropositive, but asymptomatic human T-lymphotrophic virus type 1 carriers and 18 seronegative volunteers as controls. Sagittal and transversal T2-weighted images were visually assessed for atrophy and focal cord lesions. The spinal cord cross-sectional areas and the segmental cord volumes were measured at all levels. High-resolution diffusion tensor imaging was performed in sagittal planes from the bregma down to the cervical spine. For tractography and calculation of fractional anisotropy and mean diffusivity, we used manufacturer-provided software. Two-thirds of patients showed focal lesions affecting the antero-lateral columns and in two cases also the dorsal columns. Compared to carriers and volunteers, patients presented a significant spinal cord atrophy and a reduction of fractional anisotropy (p < 0.05), correlating more to duration of symptoms than to clinical impairment. Because our carriers did not show a significant atrophy, focal lesions or a change of diffusion tensor imaging parameters, we need further long-term studies to see if these parameters at some stage may be used as early indicators of spinal cord affection in virus carriers.

Videoconferencia entre los servicios de prevención: una nueva forma de comunicación y transmisión de experiencias en el marco de un convenio de colaboración / No disponible

Objetivos: Intercambio del conocimiento, compartir equipos técnicos e incrementar la actividad científica. Metodología: Dado que parte de las tareas de los profesionales de los SPP son: evaluación de las condiciones de trabajo y la elaboración, aplicación y desarrollo de los protocolos técnicos y sanitarios, se hace imprescindible el trabajo entre los SPP, que enriquece el conocimiento y permite la transferencia científica. En julio de 2010, se aprobó un convenio de colaboración entre los SPP de los hospitales de la Santa Creu i Sant Pau (Barcelona) y la Corporació Parc Taulí (Sabadell). Resultados: Se han compartido equipos de mediciónpara la evaluación de parámetros de higiene, con criterios técnicos y asistenciales y protocolos de vigilancia de la salud. Se han instaurado las videoconferencias como sesiones periódicas entre los servicios para estrechar los vínculos y reafirmar la colaboración. Conclusiones: El trabajo entre los dos SPP permite y promueve el trabajo transversal. En sí mismo, trabajar en equipo, es un conocido factor amortiguador del riesgo psicosocial que en el caso de los equipos de los SPP, no es menospreciable. Las nuevas tecnologías ya disponibles en hospitales como herramientas de comunicación son claves para llevar a término el trabajo y la colaboración entre dos equipos diferentes, separados por la distancia. Permiten la asistencia simultánea de los dos equipos, la discusión compartida y el consenso (AU)

No disponible

Citotoxicidad del glifosato en células mononucleares de sangre periférica humana / Cytotoxicity of the herbicide glyphosate in human peripheral blood mononuclear cells

Introducción. El glifosato es un herbicida de amplio espectro, no selectivo, utilizado comúnmente en agricultura para eliminar malezas. Los estudios que han evaluado la toxicidad del glifosato en animales y en ambiente muestran que las formulaciones comerciales son más tóxicas que el componente activo. Objetivos. Evaluar la toxicidad del glifosato grado técnico y de la formulación comercial Roundup® en células mononucleares de sangre periférica humana. Materiales y métodos. Células mononucleares de sangre periférica humana fueron expuestas a diferentes concentraciones de glifosato en grado técnico y en la forma de Roundup® por 24, 48, 72 y 96 horas. La citotoxicidad se evaluó mediante el método de exclusión con azul de tripano y reducción del reactivo sal sódica de (2,3-bis[2-metoxi-4-nitro-5-sulfofenil]-2Htetrazolio-5-carboxianilida) (XTT). Resultados. Ambas presentaciones del glifosato (grado técnico y Roundup®) fueron tóxicas para las células mononucleares de sangre periférica humana. Roundup® fue más citotóxico que el glifosato grado técnico, ya que se encontró que la concentración letal 50 (LC50) analizada con el método de exclusión con azul de tripano a las 24 horas fue de 56,4 µg/ml de glifosato en la forma de Roundup® y de 1.640 mg/ml (1,64 µg/ml) para glifosato grado técnico. Conclusiones. Los resultados de este estudio in vitro confirman el efecto tóxico para las células humanas observado para el glifosato y sus preparaciones comerciales, y que estas últimas son más citotóxicas que el compuesto activo, lo que apoya la idea de que los aditivos presentes en las formulaciones comerciales juegan un papel crucial en la toxicidad atribuida a los herbicidas que contienen glifosato.

Introduction. Glyphosate is a broad-spectrum, non-selective herbicide and commonly used to eliminate weeds in agricultural and forest settings. Studies evaluating glyphosate toxicity in animals and environment show that commercial formulations of glyphosate are more toxic than the active component itself. Objectives. Technical grade glyphosate was compared with the commercial formulation Roundup® in their respective toxicities on human peripheral blood mononuclear cells. Materials and methods. Human peripheral blood mononuclear cells were exposed to different concentrations of glyphosate, either technical grade or in the form of Roundup for 24 h, 48 h, 72 h, and 96 h. Cytotoxicity was assayed by trypan blue dye exclusion method and reduction of (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2Htetrazolium-5-carboxyanilide inner salt) XTT reagent. Results. Both technical grade glyphosate and Roundup® formulation were toxic to human peripheral blood mononuclear cells. Cytotoxicity of Roundup® was higher than cytotoxicity of glyphosate, since the LC50 (50% lethal concentration) determined by the trypan blue exclusion method at 24 h was the equivalent of 56.4 ìg/ml of glyphosate in the form of Roundup® and 1,640 ìg/ml (1.64 mg/ml) for technical grade glyphosate. Conclusions. This in vitro study confirmed the toxic effects on human cells by glyphosate and its commercial preparations. Commercial formulations were more cytotoxic than the active component alone, supporting the concept that additives in commercial formulations play a role in the toxicity attributed to glyphosate-based herbicides.

[Cytotoxicity of the herbicide glyphosate in human peripheral blood mononuclear cells]. / Citotoxicidad del glifosato en células mononucleares de sangre periférica humana.

INTRODUCTION: Glyphosate is a broad-spectrum, non-selective herbicide and commonly used to eliminate weeds in agricultural and forest settings. Studies evaluating glyphosate toxicity in animals and environment show that commercial formulations of glyphosate are more toxic than the active component itself. OBJECTIVES: Technical grade glyphosate was compared with the commercial formulation Roundup in their respective toxicities on human peripheral blood mononuclear cells. MATERIALS AND METHODS: Human peripheral blood mononuclear cells were exposed to different concentrations of glyphosate, either technical grade or in the form of Roundup for 24 h, 48 h, 72 h, and 96 h. Cytotoxicity was assayed by trypan blue dye exclusion method and reduction of (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2Htetrazolium-5-carboxyanilide inner salt)XTT reagent. RESULTS: Both technical grade glyphosate and Roundup formulation were toxic to human peripheral blood mononuclear cells. Cytotoxicity of Roundup was higher than cytotoxicity of glyphosate, since the LC50 (50% lethal concentration) determined by the trypan blue exclusion method at 24 h was the equivalent of 56.4 microg/ml of glyphosate in the form of Roundup and 1,640 microg/ml (1.64 mg/ml) for technical grade glyphosate. CONCLUSIONS: This in vitro study confirmed the toxic effects on human cells by glyphosate and its commercial preparations. Commercial formulations were more cytotoxic than the active component alone, supporting the concept that additives in commercial formulations play a role in the toxicity attributed to glyphosate-based herbicides.

Abnormal expression of CD54 in mixed reactions of mononuclear cells from hyper-IgE syndrome patients.

Hyper-IgE syndrome (HIES) is a rare multisystem disorder characterized by increased susceptibility to infections associated with heterogeneous immunologic and non-immunologic abnormalities. Most patients consistently exhibit defective antigen-induced-T cell activation, that could be partly due to altered costimulation involving accessory molecules; however, the expression of these molecules has never been documented in HIES. Therefore, we investigated the expression of CD11a, CD28, CD40, CD54, CD80, CD86, and CD154 in peripheral blood mononuclear cells from six patients and six healthy controls by flow cytometry after autologous and mixed allogeneic reactions. Only the allogeneic stimuli induced significant proliferative responses and interleukin 2 and interferon gamma production in both groups. Most accessory, molecules showed similar expression between patients and controls with the exception of CD54, being expressed at lower levels in HIES patients regardless of the type of stimulus used. Decreased expression of CD54 could partly explain the deficient T cell activation to specific recall antigens in HIES patients, and might be responsible for their higher susceptibility to infections with defined types of microorganisms.

Abnormal expression of CD54 in mixed reactions of mononuclear cells from hyper-IgE syndrome patients

Hyper-IgE syndrome (HIES) is a rare multisystem disorder characterized by increased susceptibility to infections associated with heterogeneous immunologic and non-immunologic abnormalities. Most patients consistently exhibit defective antigen-induced-T cell activation, that could be partly due to altered costimulation involving accessory molecules; however, the expression of these molecules has never been documented in HIES. Therefore, we investigated the expression of CD11a, CD28, CD40, CD54, CD80, CD86, and CD154 in peripheral blood mononuclear cells from six patients and six healthy controls by flow cytometry after autologous and mixed allogeneic reactions. Only the allogeneic stimuli induced significant proliferative responses and interleukin 2 and interferon gamma production in both groups. Most accessory molecules showed similar expression between patients and controls with the exception of CD54, being expressed at lower levels in HIES patients regardless of the type of stimulus used. Decreased expression of CD54 could partly explain the deficient T cell activation to specific recall antigens in HIES patients, and might be responsible for their higher susceptibility to infections with defined types of microorganisms.

[Modulation of the expression of L-selectin by chemotactic agents and GM-CSF]. / Modulación de la expresión de la L-selectina por agentes quimiotácticos y GM-CSF.

L-selectin is an adhesion molecule with constitutive expression located on the membrane of granulocytes, monocytes and lymphocytes. It is involved in the early stages of migration of these cells toward either the sites of inflammation or lymphoid tissues. After the cells are activated, L-selectin is down-regulated with shedding of a soluble fragment. Flow cytometry was used to measure L-selectin expression levels on the granulocyte surface, after incubation with a phorbol esther (PMA), two chemotactic factors (fMLP and LTB4) and a cytokine (GM-CSF). Under basal conditions, the expression of L-selectin was found in a high percentage (95.0 +/- 0.7) of granulocytes; PMA stimulation led to a marked decrease in expression (3.2 +/- 0.6). Chemotactic factors also led to a significant decrease in L-selectin expression (69.9 +/- 5.0 for LTB4, and 53.70 +/- 4.3 for fMLP), whereas the incubation with GM-CSF produced no significant changes (89.1 +/- 4.8). When all the conditions were compared, the PMA effect was significantly higher than those observed with other stimuli; furthermore, the expression upon incubation with fMLP and LTB4 was statistically significant. These results suggest that the level of activation reached by granulocytes is directly related to their capacity for shedding L-selectin from the cell surface, and that these levels are lowered after the stimulation by chemotactic factors. GM-CSF activates several important functions of granulocyte cells, however it does not induce L-selectin shedding.

Moleculas accesorias / Accesory Molecules

En la última década se ha avanzado mucho en el conocimiento de las moléculas accesorias, proteínas de superficie celular pertenecientes a diferentes familias estructurales que intervienen de forma decisiva en el proceso de presentación antigénica, donde hacen parte de la segunda señal que conduce a la activación de los linfocitos. Clasificadas didácticamente en moléculas de adhesión, moléculas coestimuladoras y correceptores; las moléculas accesorias constituyen en la actualidad un tópico de emotivo interés investigativo por las numerosas e importantes aplicaciones que se pueden derivar de su participación en diversos mecanismos fisiológicos y fisiopatológicos del sistema inmune