RESUMO
Peptides have historically been underutilized for covalent inhibitor discovery, despite their unique abilities to interact with protein surfaces and interfaces. This is in part due to a lack of methods for screening and identifying covalent peptide ligands. Here, we report a method to identify covalent cyclic peptide inhibitors in mRNA display. We combine co- and post-translational library diversification strategies to create cyclic libraries with reactive dehydroalanines (Dhas), which we employ in selections against two model targets. The most potent hits exhibit low nanomolar inhibitory activities and disrupt known protein-protein interactions with their selected targets. Overall, we establish Dhas as electrophiles for covalent inhibition and showcase how separate library diversification methods can work synergistically to dispose mRNA display to novel applications like covalent inhibitor discovery.
Assuntos
Biblioteca de Peptídeos , Peptídeos Cíclicos , Peptídeos Cíclicos/farmacologia , Peptídeos Cíclicos/genética , RNA Mensageiro/genética , Peptídeos/genéticaRESUMO
Ecoimmunology explores how ecological factors and evolutionary processes influence immune responses across various taxa and how immune responses trade-off with other traits. Studying immune responses requires biologically meaningful immunoassays applicable to a broad range of taxa and are sensitive enough to detect changes in the immune response. Useful immunoassays should also correlate with immunocompetence and fitness. The encapsulation response, a complex immune mechanism in arthropods, serves as a robust method for ecoimmunological investigations. However, traditional methods to test the encapsulation response can require long training. This study introduces an innovative, cost-effective method for assessing the encapsulation immune response in arthropods, which simplifies the procedure by reducing the training time and skill required. Our modified device utilizes a pen and syringe assembly for inserting monofilaments into arthropod larvae. We compared our device against traditional methods. Despite the new method being 22% faster, it did not compromise the accuracy or effectiveness of the encapsulation response when compared with traditional techniques, demonstrating similar degrees of melanization and encapsulation. Our method allowed for more accessible participation by less experienced researchers, such as undergraduates, facilitating their involvement in ecoimmunological research.
Assuntos
Larva , Animais , Larva/imunologia , Larva/fisiologia , Artrópodes/fisiologiaRESUMO
MAGE proteins are cancer testis antigens (CTAs) that are characterized by highly conserved MAGE homology domains (MHDs) and are increasingly being found to play pivotal roles in promoting aggressive cancer types. MAGE-A4, in particular, increases DNA damage tolerance and chemoresistance in a variety of cancers by stabilizing the E3-ligase RAD18 and promoting trans-lesion synthesis (TLS). Inhibition of the MAGE-A4:RAD18 axis could sensitize cancer cells to chemotherapeutics like platinating agents. We use an mRNA display of thioether cyclized peptides to identify a series of potent and highly selective macrocyclic inhibitors of the MAGE-A4:RAD18 interaction. Co-crystal structure indicates that these inhibitors bind in a pocket that is conserved across MHDs but take advantage of A4-specific residues to achieve high isoform selectivity. Cumulatively, our data represent the first reported inhibitor of the MAGE-A4:RAD18 interaction and establish biochemical tools and structural insights for the future development of MAGE-A4-targeted cellular probes.
Assuntos
Antígenos de Neoplasias , Proteínas de Neoplasias , Neoplasias , Antígenos de Neoplasias/química , Dano ao DNA , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Humanos , Masculino , Proteínas de Neoplasias/antagonistas & inibidores , Proteínas de Neoplasias/química , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Neoplasias/patologia , Peptídeos Cíclicos/química , Peptídeos Cíclicos/farmacologia , Relação Estrutura-Atividade , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismoRESUMO
Two types of quantitative response to the F-B strain of Friend virus in segregating generations of a cross involving a susceptible (DBA/2 or BALB/c; H-2(2)) and a resistant (C57BL/6; H-2(b)) mouse strain show a marked correlation with the H-2 type of the mice. Essential susceptibility, as determined by the splenomegalic response to high virus doses, is controlled by a single pair of alleles which segregates independently with respect to the H-2 locus. However, relative susceptibility, as determined by the incidence of the splenomegalic response at moderate or low levels of virus dosage, is significantly greater among mice homozygous or heterozygous for the H-2(d) allele than among H-2(b) homozygotes in these populations. In addition, the incidence of recovery from splenomegaly induced by a given level of virus dosage is significantly greater in H-2(b) homozygotes than in segregants of other H-2 types among their littermates. Possible mechanisms responsible for these effects are discussed.
Assuntos
Vírus da Leucemia Murina de Friend , Leucemia Experimental/etiologia , Alelos , Animais , Homozigoto , Leucemia Experimental/genética , Camundongos , Fenótipo , Esplenomegalia/etiologiaRESUMO
Cell lines have been established in culture from Friend virus-induced tumors of BALB/c (H-2d) and congenic BALB/c-H-2b (BALB.B) origin. Spleens from virus-infected hosts in the terminal stages of erythroleukemic disease provided tissues for the establishment of subcutaneously transplantable tumors of both strains. Subsequently cells of these tumors were introduced into culture and passed serially. Complete, infectious Friend virus (FV) has been routinely recovered from culture supernates of BALB.B tumor cells (HFL/b) throughout its 2-yr passage history. However, after only a few transfer generations in culture BALB/c tumor cells (HFL/d) became nonproducers of virus detectable in either the spleen focus assay in vivo or the XC assay in vitro. Nonproducer HFL/d cells possessed the complete genomes of the components of the FV complex, since FV could be recovered from them either by cocultivation with helper virus-infected syngeneic embryo fibroblasts or by serial passage in the ascitic form in normal, syngeneic adult hosts.
Assuntos
Linhagem Celular , Vírus da Leucemia Murina de Friend , Antígenos de Histocompatibilidade/análise , Animais , Nucléolo Celular , Cromatina , Feminino , Genótipo , Vírus Auxiliares , Injeções Subcutâneas , Leucemia Eritroblástica Aguda/microbiologia , Camundongos , Camundongos Endogâmicos BALB C , Mitose , Transplante de Neoplasias , Baço/patologia , Neoplasias Esplênicas , Cultura de VírusRESUMO
Cytolytic T lymphocytes (CTL) were generated against murine tumors induced by Gross, Friend, or Rauscher leukemia virus (LV) in syngeneic mixed leukocyte-tumor cell cultures. Analogous to the patterns of specificity observed with antibodies to LV-induced cell surface antigens, CTL could be classified into two major groups of specificity. Tumor cells induced by Friend, Moloney, or Rauscher virus and positive for the FMR antigen were killed by syngeneic CTL immune to any one of these three LV; the same CTL, however, were incapable of killing syngeneic tumor cells induced by Gross LV. The converse was true for Gross LV-specific CTL: these CTL were specific for syngeneic tumor cells expressing the Gross virus-associated cell-surface antigen (GCSA), and not the FMR antigen. The H-2 specificities of the two groups of LV-immune CTL were also compared, because in both cases, CTL were restricted in their killing activity to H-2-identical tumor target cells. When CTL from single strains of mice were generated against syngeneic FMR- or GCSA-positive tumor cells, differences were observed with respect both to the requirement for the expression of compatible H-2K or H-2D specificities, and to the intensity of the CTL response in congenic mice of the H-2b, H-2d, and H-2k haplotypes.
Assuntos
Vírus AKR da Leucemia Murina/imunologia , Antígenos Virais , Citotoxicidade Imunológica , Epitopos , Antígenos H-2/genética , Células Matadoras Naturais/imunologia , Animais , Antígenos de Neoplasias , Vírus da Leucemia Murina de Friend/imunologia , Genótipo , Leucemia Experimental/imunologia , Teste de Cultura Mista de Linfócitos , Camundongos , Camundongos Endogâmicos BALB C/imunologia , Camundongos Endogâmicos C57BL/imunologia , Vírus Rauscher/imunologiaRESUMO
Reciprocal bone marrow transfers were performed between mouse strains sensitive or resistant to 3-methylcholanthrene-induced thymic lymphoma. Sensitivity and resistance are properties inherent in bone marrow, and cannot be altered by maturation of marrow in an environment of the opposite phenotype.
Assuntos
Células da Medula Óssea , Resistência a Medicamentos , Linfoma/genética , Metilcolantreno , Animais , Quimera , Linfoma/induzido quimicamente , Camundongos , Camundongos Endogâmicos , FenótipoRESUMO
B10.A(5R) mice (H-2i5), immunized with spleen cells from congenic B10 mice (H-2b), responded to alloantigens of the H-2Db region by producing antibodies of only IgM type. In contrast, they produced both IgM and IgG antibodies when immunized with noncongenic H-2b cells that carry other foreign cell surface antigens (non-H-2) in addition to H-2Db. A hypothesis was proposed comparing the H-2Db antigen on a congenic cell to a hapten on a nonimmunogenic carrier which fails to induce T-cell helper function responsible for the switch from IgM to IgG secretion in B cells. Data presented here confirmed this hypothesis. 5R mice rendered tolerant to the relevant non-H-2 antigens were unable to mount the anti-H-2Db IgG response in a noncongenic immunization. Tolerance induction did not lead to abrogation of the T-cell mediated cytotoxicity.
Assuntos
Formação de Anticorpos , Antígenos de Histocompatibilidade , Animais , Tolerância Imunológica , Imunidade Celular , Imunoglobulina G/biossíntese , Imunoglobulina M/biossíntese , Camundongos , Camundongos Endogâmicos , Propriedades de Superfície , Linfócitos T/imunologiaRESUMO
B10.A(5R) mice immunized with C57BL/10 spleen cells demonstrate a normal T-cell-mediated cytotoxicity to H-2Db tumor cells but they do not mount any IgG antibody response to H-2Db alloantigens. B10.A(5R) mice do show a high titered IgG response when immunized with A.BY cells, which differ at H-2Db plus non-H-2 cell surface antigens, or with B10.A(2R) cells, which differ at H-2Db, H-2Kk, and H-2Ik cell surface antigens. These findings indicate a failure of the T-helper cells to induce the switch from IgM to IgG when the H-2Db alloantigens are the only difference on the immunizing cell. In immunizing H-2d mice with congenic H-g2 cells which differ only in the H-2Db region, mice of the C57BL/10 background made only IgM antibodies whereas mice of the BALB/c background made IgG antibodies. This comparison confirms that genes separate from H-2 regulate the T-cell helper function. The genes that influence the T-cell helper function do not regulate the T-cell-mediated cytotoxicity.
Assuntos
Formação de Anticorpos , Genes Reguladores , Antígenos de Histocompatibilidade , Linfócitos T/imunologia , Animais , Anticorpos/análise , Reações Antígeno-Anticorpo , Líquido Ascítico/citologia , Líquido Ascítico/imunologia , Membrana Celular/imunologia , Proteínas do Sistema Complemento , Testes Imunológicos de Citotoxicidade , Haploidia , Imunidade Celular , Imunoglobulina G , Imunoglobulina M , Leucemia/imunologia , Leucemia/patologia , Linfonodos/citologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Baço/citologiaRESUMO
Leukocyte fractions extracted from the tumor mass and the lymphoid organs of C57BL/6 (B6) mice carrying murine sarcoma virus-induced tumors contained primed cytolytic T-lymphocyte (CTL) precursor cells, in addition to active cytotoxic T cells. These leukocyte fractions gave a secondary response when stimulated in vitro with syngeneic tumor cells, generating large numbers of specific CTL. The activity of these CTL (H-2b) was apparently H-2-restricted, because it was ineffective on tumor targets bearing strongly cross-reacting tumor-specific antigens but with the H-2d haplotype. Furthermore, only H-2b cells bearing the Friend, Moloney, Rauscher-associated antigen, such as Rauscher leukemia virus-induced RBL-5 cells and Friend leukemia virus-induced HFL/b cells, were lysed efficiently. B male GV cells (H-2b cells induced by Gross leukemia virus) were not affected by the same CTL. We propose the existence of a dynamic state involving the migration of primed CTL precursor cells between the lymphoid organs and the tumor mass, as well as the differentiation of these precursor cells within the tumor mass into highly specific CTL.
Assuntos
Citotoxicidade Imunológica , Sarcoma Experimental/imunologia , Linfócitos T/imunologia , Animais , Antígenos de Neoplasias , Diferenciação Celular , Movimento Celular , Complexo Principal de Histocompatibilidade , Camundongos , Vírus do Sarcoma MurinoRESUMO
The HFL/b tumor cell line, induced by Friend erythroleukemia virus in BALB.B mice, was used to study the relation between virus production or nonproduction and the antigens recognized by Friend virus-specific cytolytic T lymphocytes (CTL). Analysis of clones and subclones of these tumor cells revealed a high degree of heterogeneity with respect to the production and release into culture fluids of infectious Friend virus in vitro, ranging from high levels to low or undetectable levels of virus production. Although no major differences could be detected among the antibody-defined serotypes of the various clones, the susceptibility of cells of individual HFL/b clones to attack by Friend virus-specific CTL varied widely, and those clones which produced large amounts of infectious virus provided the most sensitive target cells. It was also apparent that production of infectious Friend virus was inhibitory to CTL generation in syngeneic mixed leukocyte-tumor cell cultures. Friend erythroleukemia virus-producing cells thus appeared to interact in a complex manner with the host CTL response by modulating their production of infectious Friend virus.
Assuntos
Vírus da Leucemia Murina de Friend/imunologia , Imunidade Celular , Leucemia Eritroblástica Aguda/imunologia , Linfócitos T/imunologia , Replicação Viral , Animais , Antígenos de Neoplasias/análise , Antígenos de Superfície/análise , Células Clonais , Citotoxicidade Imunológica , Relação Dose-Resposta Imunológica , Leucemia Eritroblástica Aguda/microbiologia , Leucemia Experimental/imunologia , CamundongosRESUMO
We have constructed a series of "synthetic" target cell lines for an analysis of the specificity of anti-Friend virus (FV) CTL. Our results show that murine H-2 genes and individual retroviral genes can be stable expressed in Fisher rat embryo (FRE) cells, and that their products have the potential to form target structures recognized by mouse CTL. Cells expressing H-2Db and either the env or gag genes of one component of FV, helper Friend murine leukemia virus (FMuLV), were lysed by anti-FV CTL and by CTL generated against FMuLV alone. Experiments with Db-transfected FRE clones infected only with the replication-defective spleen focus-forming virus (SFFV) component of FV indicate that the SFFV genome also provides specificities recognized by both anti-FV and anti-FMuLV CTL, thus demonstrating the existence of a crossreactive CTL population. An unexpected finding was that anti-FMuLV CTL, but not anti-FV CTL were also able to lyse FRE clones that expressed H-2Kb in either the presence or absence of FV. The use of heterologous cell lines for the construction of synthetic target cells thus offers a useful approach for the analysis of T cell specificity.
Assuntos
Epitopos/genética , Vírus da Leucemia Murina de Friend/imunologia , Proteínas dos Retroviridae/genética , Linfócitos T Citotóxicos/imunologia , Proteínas do Envelope Viral/genética , Animais , Células Clonais/imunologia , Citotoxicidade Imunológica , Epitopos/imunologia , Feminino , Fibroblastos/metabolismo , Produtos do Gene gag , Genes Virais , Antígenos H-2/genética , Antígenos H-2/imunologia , Leucemia Eritroblástica Aguda/genética , Leucemia Eritroblástica Aguda/imunologia , Leucemia Eritroblástica Aguda/microbiologia , Camundongos , Camundongos Endogâmicos BALB C , Ratos , Ratos Endogâmicos F344 , Proteínas dos Retroviridae/imunologia , Transfecção , Proteínas do Envelope Viral/imunologiaRESUMO
The N-B locus affecting tissue culture infectivity with naturally occurring murine leukemia viruses appears to be identical to the Fv-1 locus described for sensitivity to Friend leukemia virus. Results of tissue culture studies were parallel to results of studies in vivo and indicate that the F-S virus is N-tropic and the F-B virus is NB-tropic. Inbred and partially congenic mouse strains sensitive at Fv-1 show N-type sensitivity; strains resistant at Fv-1 show B-type sensitivity. The Fv-2 locus does not appear to exert significant effect in tissue culture. Knowledge of N-B type has been useful in predicting Fv-1 sensitivity.
Assuntos
Vírus da Leucemia Murina de Friend/imunologia , Genes Dominantes , Vírus da Leucemia Murina/imunologia , Animais , Técnicas de Cultura , Efeito Citopatogênico Viral , Embrião de Mamíferos/citologia , Imunogenética , Endogamia , Vírus da Leucemia Murina/patogenicidade , CamundongosRESUMO
The Fv-1 gene, which regulates sensitivity of mouse cells to infection by naturally occurring host-range types of murine leukemia virus, was shown to be located on linkage group VIII (chromosome 4), 39 map units from b.
Assuntos
Vírus da Leucemia Murina de Friend/imunologia , Genes , Leucemia Experimental/imunologia , Alelos , Animais , Mapeamento Cromossômico , Cor , Cruzamentos Genéticos , Vírus da Leucemia Murina de Friend/isolamento & purificação , Ligação Genética , Cabelo , Hibridização Genética , Imunidade , Imunogenética , Leucemia Experimental/etiologia , Camundongos , Baço/microbiologiaRESUMO
When B10.A (5R) mice (H-12i5) are immunized with spleen cells from congenic B10 mice (H-12b), they respond to alloantigens of the H-2Db region by producing antibodies of only IgM type. In contrast, they produce both IgM and IgG antibodies when immunized with A.BY cells (H-2b) that carry other foreign cell surface antigens (non-H-2) in addition to H-2Db. Preimmunization of 5R mice with two injections of congenic cells leads to an H-2Db specific inhibition of the IgG response to a subsequent immunization with A.BY cells. It is concluded that congenic B10 cells fail to activate helper T cells which are necessary to induce the switch from IgM to IgG production. Instead T- or B-cell tolerance may be induced with prohibits the subsequent IgG response to A.BY cells, possibly by way of suppressor T cells which may act either on B cells directly or via helper T cells.
Assuntos
Formação de Anticorpos , Genes , Antígenos de Histocompatibilidade , Imunoglobulina G/biossíntese , Animais , Imunoglobulina M/biossíntese , Linfócitos/imunologia , Camundongos , Camundongos Endogâmicos , Modelos BiológicosRESUMO
BALB/c-H-2b (BALB.B) mice are less susceptible to the Friend virus (FV) disease syndrome than congenic BALB/c (H-2d) mice, and spleen cells from FV-infected BALB.B mice are markedly less tumorigenic on transplantation to syngeneic hosts than those from FV-infected BALB/c mice. For these reasons we investigated the expression of FV-associated cell surface antigens on cultured, FV-trnasformed cell lines of BALB.B and BALB/c origin. Both cell lines induced transplantation immunity in syngeneic hosts toward further implantations of the same tumor, BALB.B cells being significantly more potent in this respect than BALB/c cells. BALB.B tumor cells, which produce complete, infectious FV, expressed both the cell surface antigen, FMR (corresponding to the cytotoxic antibodies in anti-FV antisera), and virus envelope antigen (VEA, corresponding to the virus-neutralizing antibodies in the anti-FV antisera). BALB/c tumor cells, on the other hand, which are FV-nonproducers, expressed no FMR antigen, but did express VEA on their surfaces for at least 100 passages in culture. These cells could induce FV-neutralizing but not cytotoxic anti-FMR antibodies when used to immunize syngeneic hosts. The absence of FMR antigen may be the basis for the reduced capacity of BALB/c tumor cells, by comparison with BALB.B tumor cells, to induce transplantation immunity. After about the 125th serial transfer in culture, BALB/c tumor cells spontaneously ceased to express VEA and simultaneously became very weak inducers of transplantation immunity in BALB/c hosts. This loss of VEA did not stem from the loss of either the spleen focus-forming virus or the helper virus genomes from these cells, since both viruses could still be recovered from the cell line.
Assuntos
Antígenos , Vírus da Leucemia Murina de Friend/imunologia , Neoplasias Experimentais/imunologia , Baço/imunologia , Animais , Antígenos de Neoplasias , Antígenos Virais , Linhagem Celular , Camundongos , Camundongos Endogâmicos BALB C/imunologia , Transplante de Neoplasias , Baço/transplante , Imunologia de Transplantes , Transplante HomólogoRESUMO
This report characterizes the intra-H-2 crossover in the D2.GD mouse strain. Recombination occurred within the I region between the immune response (Ir) gene controlling immune responsiveness to ragweed extract (RE). Ir-RE, and the Ir gene governing responsiveness to the random linear terpolymers of glutamic acid and lysine with either tyrosine or pheylalanine (Ir-GLT and Ir-GLphi). The Ir-RE gene was tentatively located in the Ir-1A subregion and the Ir-GLT and Ir-GLphi gene(s) tentatively placed in the Ir-1B subregion. The importance of this recombinant strain to further studies on the fine structure of the I region is discussed.
Assuntos
Mapeamento Cromossômico , Genes , Isoantígenos , Recombinação Genética , Alérgenos , Animais , Formação de Anticorpos , Troca Genética , Ligação Genética , Genótipo , Antígenos de Histocompatibilidade , Imunização , Imunoglobulina E/análise , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Anafilaxia Cutânea Passiva , Plantas , Polímeros/imunologiaRESUMO
Females of the RF and SJL inbred mouse strains transmit to their progeny of both sexes a nonmendelian maternal resistance factor (MRF) able to suppress the expression of endogenous ecotropic murine leukemia virus (E-MuLV). This MRF is demonstrable in crosses with AKR mice by comparing E-MuLV expression in the spleens and thymuses of reciprocal F1 generations. DBA/2 and ST/b mice are MRF negative by these criteria. Neonatal inoculation of E-MuLV-containing spleen extracts gives rise to persistent expression of infectious virus in mice of the MRF- but not the MRF+ strains. However, inoculation of the virus in 30-d-old females of the MRF- strains no longer leads to a state of persistent infection; instead, these females become MRF+ and transmit protection against E-MuLV expression to their progeny by AKR and RF males. The MRF appears to be transmitted to the progeny mainly through the milk, since foster-nursing AKR neonates on RF (but not DBA/2) mothers greatly reduces E-MuLV expression in the progeny. These RF-fostered AKR mice also show a reduced and delayed lymphoma incidence, a finding consistent with the idea that maternally transmitted resistance to E-MuLV expression is the basis for the classic maternal resistance to lymphomagenesis seen in the progeny of RF mothers.
Assuntos
Leucemia Experimental/genética , Linfoma/genética , Troca Materno-Fetal , Camundongos Endogâmicos/genética , Envelhecimento , Animais , Animais Lactentes , Cruzamentos Genéticos , Feminino , Imunidade Inata , Vírus da Leucemia Murina/crescimento & desenvolvimento , Leucemia Experimental/microbiologia , Linfoma/microbiologia , Camundongos , Camundongos Endogâmicos AKR , Camundongos Endogâmicos DBA , Fenótipo , Gravidez , Baço/microbiologia , Ensaio de Placa ViralRESUMO
Friend murine leukemia virus (FV), isolated from infectious serum of several mouse strains, has been examined for the presence of H-2 antigens. Following banding of the virus on a discontinuous sucrose gradient, pelleting, and disruption with Nonidet P-40 detergent, virus preparations were tested for their capacity to inhibit the lysis of target cells mediated by various anti-H-2K or anti-H-2D antisera. Virus from mice homozygous for the H-2b, H-2d, H-2g H-2k, and H-2ol haplotypes or heterozygous for the H-2g/H-2k, H-2b/H-2d, and H-2b/H-2k haplotypes was used. Of the six H-2D or H-2K alleles examined, the products of only two, H-2Db and H-2Kk were detected. Virus preparations contained no, one, or both antigens, depending on the genotype of the host animal. Control preparations from normal mouse serum and preparations in which the virus had not been disrupted demonstrated no H-2 activity. Furthermore, attempts to neutralize FV spleen focus forming activity with anti-H-2Db or anti-H-2Kk antisera yielded negative results.
Assuntos
Antígenos Virais/análise , Vírus da Leucemia Murina de Friend/imunologia , Antígenos H-2/análise , Leucemia Experimental/imunologia , Animais , Membrana Celular/imunologia , Membranas/imunologia , Camundongos , Camundongos EndogâmicosRESUMO
At 37 degrees C, fluorescein-conjugated anti-H-2 alloantibodies specifically induce, at the surface of living mouse lymphocytes, the redistribution of the corresponding H-2 antigens, which cluster as patches and sometimes single caps at one pole of the cell. This aggregation is inhibited at 0 degrees C and the H-2 antigens, stained by fluorescent antibodies in the cold, appear evenly spread over the cell surface. This phenomenon was used to define the relationships between the membrane structures bearing the antigens coded by the H-2K and the H-2D genes of the H-2 region. Monospecific anti-H-2 antibodies coupled to either tetramethyl rhodamine isothiocyanate or fluorescein isothiocyanate were used to induce the redistribution of H-2D and H-2K antigens of the H-2(b) and H-2(k) haplotype at the surface of lymph node cells from homozygous and F(1) hybrid mice. It was observed that the diffuse distribution of H-2K antigens labeled at 0 degrees C was not affected by the prior antibody-induced aggregation of H-2D antigens and vice versa. The results were the same for H-2 antigens governed by genes located either in cis or in trans position. These data indicate that the H-2K and H-2D antigens migrate independently at the cell surface, and suggest that the gene products from the D and the K end of the H-2 region are expressed on independent molecules or structures at the cell membrane.