Functional characteristics of Peyer's patch cells. III. Carrier priming of T cells by antigen feeding.

Peyer's patch T cells may serve an important role in the interaction of the host with intraluminal gut antigens. Studies presented in this paper demonstrate that T cells in murine Peyer's patches can be carrier primed for helper function in the induction of an antihapten response by feeding antigen. Carrier priming was assessed by measuring the ability of Peyer's patch cells from mice fed heterologous erythrocytes to enhance an antitrinitrophenyl (TNP) response in vitro when added to normal Peyer's patch cells cultured with TNP coupled to the erythrocyte used for feeding. Priming of T helper cells in Peyer's patches was antigen specific and occurred when erythrocytes were administered orally but not when erythrocytes were injected intravenously or intraperitoneally. Murine Peyer's patches are naturally deficient in a cooperating accessory adherent cell type(s) required for B-cell induction to humoral antibody synthesis in vitro and antigen feeding does not result in significant induction of Peyer's patch B cells to humoral antibody synthesis in vivo. Since Peyer's patch T cells can be carrier-antigen primed for helper function in the absence of B-cell induction to humoral antibody synthesis, these studies may indicate that T-cell priming is less dependent than B-cell induction on cooperating accessory adherent cells.

Functional characteristics of Peyer's patch lymphoid cells. I. Induction of humoral antibody and cell-mediated allograft reactions.

Peyer's patches from normal mice contain antigen-sensitive B and T cells, but lack the accessory adherent cell type(s) required both for the induction of humoral immune responses and for the induction of allograft reactions against cell surface alloantigens. Immune responsiveness can be restored to cultures of Peyer's patch cells by the addition of either APEC or ME. Peyer's patch B cells can be specifically induced by antigen to synthesize humoral antibody. Peyer's patch T cells can cooperate in B-cell induction and can be induced to mediate an allograft reaction against an allogeneic stimulus. Peyer's patch lymphoid aggregates appear to be a storehouse of antigen-sensitive cells sequestered in such a way as to lack an accessory cell type or factor required for induction,

Functional characteristics of Peyer's patch lymphoid cells. II. Lipopolysaccharide is thymus dependent.

This study shows that LPS is not mitogenic in cultures containing B cells, or B cells and accessory adherent cells or ME, unless T cells are present. This observation rules out models of induction of antibody synthesis in which it is assumed that the delivery of a mitogenic signal by the interaction of LPS with the membrane of the B cell is in itself sufficient for B-cell induction (19). Further, it makes unlikely the proposed extrapolation of such a model to other so-called thymus-independent antigens, e.g., PVP, levan, dextran, and SIII (19). The mitogenic action of LPS appears to be due to its ability to complete an inductive stimulus to B cells (13). We interpret the observed thymus dependence of the B-cell response to LPS in light of a model in which two signals are obligatory for B-cell induction (14). The first signal in the inductive pathway is delivered to the antigen-sensitive cell via a conformational change in the receptor upon interaction with antigen. The second signal is delivered via the thymus-derived cooperating system. Since LPS can induce immune responses to both immunogenic and nonimmunogenic ligands (9-13) we envision that one signal is delivered to the B cell via specific binding of the ligand to the B-cell antigen receptor, while a second signal is delivered as a result of T-cell cooperation via membrane-bound LPS. This has been termed abnormal induction (20). In this example LPS is the foreign membrane-bound determinant in question although histocompatibility antigens (21, 22), viral determinants, or surface bound lectins could act similarly. In light of the above model, one observation should be pointed out. LPS inhibits the induction of a SRBC response in normal Peyer's patch cells to which adherent cells or ME is added. This inhibition appears to be a T-cell-mediated effect because it is abolished by partial depletion of the T-cell population by antitheta treatment. Since the induction of IgM producing PFC is being measured, the T-cell-dependent LPS inhibition could act either (a) by induction of T-cell "suppression" (23, 24) of the normal cooperating system required for a SRBC response, or (b) by the induction of such high levels of cooperating function (13) as to be inhibitory to a SRBC IgM response. Our observations contrast sharply with prior reports which describe LPS as a thymus-independent antigen (2-4) and a B-cell mitogen (5-8) capable of stimulating immune responses in the absence of T-cell cooperation (2-12). This demonstration of the thymus dependence of LPS stimulation has been possible because Peyer's patches from congenitally athymic (nude) mice are functionally a highly purified B-cell population devoid of T cells and accessory adherent cells. In this respect, earlier studies relied on nude spleen cultures and spleen cultures from thymectomized, lethally irradiated, and bone marrow-reconstituted mice (3, 4, 6-13). These spleen cultures which contain B cells and accessory adherent cells are recognized to be deficient but not devoid of the thymus-derived contribution to the inductive stimulus (12, 13). It could be argued that the presence of T cells and adherent cells is in fact required for the antigen-specific effect and not for the LPS effect. However, this is unlikely since our experiments show that LPS is not directly mitogenic for B cells and does not stimulate background anti-SRBC PFC. It seems unlikely that Peyer's patch antigen-sensitive cells differ from antigen-sensitive cells in the spleen in their mechanism of induction. We have shown that Peyer's patch B cells can be specifically induced by antigen, and Peyer's patch T cells mediate cooperating and killer functions. Alternately, the possibility that Peyer's patch B cells were not stimulated by LPS as a result of prior cryptic exposure to LPS (13) in the intestinal tract was excluded since cultures containing B cells, T cells, and adherent cells or ME were stimulated to DNA synthesis by LPS. The reason that certain antigens appear to be thymus independent may be that their repeating polymeric nature permits inductive interactions at very low levels of thymus-derived cooperation (see reference 20 for quantitative considerations). It has been stated that the inductive properties of all thymus-independent antigens are directly related to their ability to act as B-cell mitogens (19). The observation that LPS is thymus dependent for its B-cell mitogenic activity makes us question the thymus independence of any antigen.

Vicia villosa agglutinin separates freshly isolated Peyer's Patch T cells into interleukin 5- or interleukin 2-producing subsets.

Murine L3T4 T cells freshly isolated from Peyer's Patch were fractionated based on differential adherence to Vicia villosa agglutinin (VVA). VVA adherent cells secreted IL-5, but not IL-2, after stimulation with Con A and IL-1. In striking contrast, VVA nonadherent PP L3T4 T cells secreted IL-2, but not IL-5, under the same conditions. In addition, supernatants from VVA adherent, but not from VVA nonadherent cells cultures, enhanced IgA secretion by LPS-stimulated splenic B cells to the same extent as purified IL-5. Thus, IL-5-producing T cells are present in PP in situ and may play an important role in the development of mucosal immunity. Further, differential adherence to VVA can be used to separate T cell populations that preferentially secrete IL-5 or IL-2.

Nonspecific recruitment of cytotoxic effector cells in the intestinal mucosa of antigen-primed mice.

We have examined cytotoxic responses of lymphocytes derived from the gut epithelium of mice primed systemically and enterically with alloantigens. Both gut intraepithelial (IEL) and splenic lymphocytes from alloantigen-primed mice were found to contain antigen-specific cytotoxic T cell activity. However, after priming, gut IEL also developed high levels of natural killer and spontaneous cytotoxic cell activities. We suggest that this nonspecific activation of additional cytotoxic effector populations during an antigen-specific response is an important host immune defense within the intestinal mucosa.

An HLA-D region restriction fragment length polymorphism associated with celiac disease.

This study is the first to describe a molecular marker that distinguishes the celiac disease HLA-D region haplotype from a serologically identical haplotype in unaffected controls. Using a DQ beta chain cDNA probe and the restriction endonuclease Rsa I, we have detected a polymorphic 4.0 kb fragment which, in DQw2 individuals, is associated with a 40-fold increased relative risk of developing celiac disease. This finding should permit the identification of the celiac disease susceptibility gene(s) in the HLA-D region and facilitate a more precise dissection of the molecular and immunogenetic mechanisms involved in the pathogenesis of that disease.

The V delta 1 T cell receptor repertoire in human small intestine and colon.

V delta 1 bearing T cells comprise the major population of gamma/delta T cells in the human intestinal tract. To gain insight into mechanisms involved in the generation of these cells and the diversity of their repertoire, we have characterized the junctional sequences of V delta 1 T cell receptor transcripts in the human small intestine and colon. Mucosal biopsies obtained from defined regions along the length of the small intestine or colon contained a high frequency of either one or a few identical in frame V delta 1 sequences. Less abundant sequences were also detected repeatedly throughout the length of small intestine or colon. Moreover, the intestinal V delta 1 repertoire in the small intestine and colon appeared compartmentalized and showed no overlap with the V delta 1 repertoire in peripheral blood. Dominant V delta 1 transcripts in each subject differed between the small intestine and colon, and the dominant transcripts within these sites differed among individuals. Analysis of small intestinal transcripts obtained at a 1-yr interval revealed that the V delta 1 repertoire was stable over time. The fact that the majority of V delta 1 transcripts, both dominant and rare, are distributed throughout a several meter length of the adult intestinal tract and are stable over time suggests they are not generated by an ongoing process of in situ VDJ gene rearrangement. Our results favor a model in which the repertoire of V delta 1 T cells in the intestinal tract is shaped by positive selection in response to a limited array of ligands before the migration of V delta 1 cells throughout the small intestine or colon.

Possible role for a human adenovirus in the pathogenesis of celiac disease.

Celiac disease in humans is activated by the dietary ingestion of wheat, rye, triticale, barley, and possibly oats. Gliadins in wheat and similar proteins in the other grains are known to activate disease in susceptible individuals. There is a striking association between celiac disease and HLA-B8, -DR3 and/or -DR7, and -DC3. Nonetheless, less than 0.2% of individuals with those serologic HLA specificities develop celiac disease and disease is not always concordant among monozygotic twins. We propose that additional environmental factors may be important in the pathogenesis of celiac disease. To investigate that possibility, we examined a data bank of protein sequences for other proteins that might share amino acid sequence homologies with A-gliadin, an alpha-gliadin component known to activate celiac disease and whose complete primary amino acid sequence is known. These studies demonstrate that A-gliadin shares a region of amino acid sequence homology with the 54-kD E1b protein of human adenovirus type 12 (Ad12), an adenovirus usually isolated from the intestinal tract. The region spans 12 amino acid residues, includes 8 residue identities and an identical pentapeptide, and is hydrophilic in both proteins. Antibody reactive with the 54-kD Ad12 E1b protein cross-reacts with A-gliadin, a 119 amino acid cyanogen bromide peptide of A-gliadin that spans the region of homology and a synthetic heptapeptide of A-gliadin from within the region of homology. We suggest that an encounter of the immune system with antigenic determinants produced during intestinal viral infection may be important in the pathogenesis of celiac disease.

Identification of nuclear receptors for VIP on a human colonic adenocarcinoma cell line.

Vasoactive intestinal peptide (VIP) is a neuropeptide with broad tissue distribution. Although its precise function is unknown, it is thought to exert its effect, at least in part, by interacting with cell surface receptors. Nuclear receptors for VIP have now been identified by specific binding of 125I-labeled VIP to nuclei of a human colonic adenocarcinoma cell line (HT29) and by cross-linking of 125I-labeled VIP to its receptor on intact nuclei. In contrast, 125I-labeled transferrin shows only background binding to nuclei but significant binding to intact cells. Purity of the isolated nuclei was further substantiated by electron microscopy. The apparent molecular sizes of the VIP--cross-linked nuclear and cell surface receptors are similar but not identical.

Identification of c-fos-responsive elements downstream of TAR in the long terminal repeat of human immunodeficiency virus type-1.

Activation of HIV-1 requires the binding of host cell transcription factors to cis elements in the proviral long terminal repeat (LTR). This study identifies c-fos-responsive sequence motifs in the U5 transcribed noncoding leader sequences downstream of the viral transactivator responsive (TAR) element. These DNA sequence motifs are the most downstream regulatory elements described thus far in the HIV-1 LTR. Functional studies, using human colon epithelial cell lines, demonstrate that the downstream elements are transactivated by expression of the c-fos protooncogene and can transmit PMA and TNF alpha activation signals to the viral LTR. Moreover, the c-fos-responsive elements mediate HIV-1 LTR transcription independent of Tat and the NF kappa B-binding enhancer element. Nuclear extracts of colon epithelial cells form distinct gel mobility shift complexes with the c-fos-responsive elements. These complexes comigrate with a gel shift complex formed on a classical CRE oligonucleotide and are competed by CRE oligonucleotides. These data indicate that the HIV-1 LTR contains previously unrecognized functional DNA cis-regulatory elements downstream of TAR in the transcribed noncoding 5' leader sequence and suggest that early response genes such as c-fos play a role in the activation of HIV-1 gene expression.

The delta T cell receptor repertoire in human colon and peripheral blood is oligoclonal irrespective of V region usage.

The majority of gamma/delta T cell receptors (TCR) in the human intestinal mucosa are thought to use the TCRDV1 (V delta 1) variable region gene segment, whereas gamma/delta T cells in the circulation predominantly express the TCRDV2 (V delta 2) gene segment. delta T cell receptors that use the TCRDV2 variable region gene segment generally have been regarded as highly diverse, whereas those that use the TCRDV1 gene segment are oligoclonal, whether present in the intestinal tract or in peripheral blood. We report herein that oligoclonality is a general feature of the peripheral delta T cell receptor repertoire in healthy human adults, irrespective of the variable region used and regardless of whether gamma/delta T cells reside in the intestinal mucosa or in peripheral blood. In addition, the delta T cell receptor repertoire is shown to be highly compartmentalized between such sites as the colon and peripheral blood, relatively stable over at least a 10-16-mo period, and unique in each individual. Further, the spectrum of variable region genes used by delta T cell receptor transcripts in the human colon is greater than previously recognized. Thus, in addition to the TCRDV1 and TCRDV2 variable region gene segments, delta T cell receptors in normal intestinal mucosa can use TCRDV3 (V delta 3) and TCRAV (V alpha) gene segments which, in some individuals, comprise a significant component of the mucosal delta T cell receptor repertoire. Our studies indicate that the potential of delta T cell receptors for extensive diversity is not reflected in the mature human repertoire. Moreover, these findings suggest a model wherein the delta T cell receptor repertoire in the colon and peripheral blood is shaped by selection and clonal expansion of gamma/delta T cells that ultimately seed throughout the length of the colon mucosa and populate the circulation.

Entamoeba histolytica trophozoites induce an inflammatory cytokine response by cultured human cells through the paracrine action of cytolytically released interleukin-1 alpha.

Infection with the protozoan parasite Entamoeba histolytica results in a high mortality worldwide. To initiate infection, E. histolytica trophozoites in the bowel lumen penetrate the epithelium, and cause extensive lysis of host cells. The acute amebic lesions in animal models are characterized by infiltration with inflammatory cells, particularly neutrophils. The acute host response is likely important for determining whether the infection will spread systemically, but little is known regarding the signals which initiate an acute inflammatory response to E. histolytica. In the studies reported herein, we used an in vitro model system to define the proinflammatory signals produced by epithelial and other host cells in response to infection with E. histolytica trophozoites. Coculture of human epithelial and stromal cells and cell lines with trophozoites is shown to increase expression and secretion of an array of chemoattractant and proinflammatory cytokines, including IL-8, GRO alpha, GM-CSF, IL-1 alpha, and IL-6. Moreover, high-level secretion of those cytokines is regulated by the paracrine action of cytolytically released IL-1 alpha. A second mechanism for trophozoite-induced IL-8 production involves trophozoite-target cell contact via a galactose-inhibitable amebic adherence protein, and appears to be mediated through increased intracellular calcium levels. These studies define novel mechanisms through which acute inflammation can be initiated in the host in response to a cytolytic pathogen, such as E. histolytica.

Infection of human intestinal epithelial cells with invasive bacteria upregulates apical intercellular adhesion molecule-1 (ICAM)-1) expression and neutrophil adhesion.

The acute host response to gastrointestinal infection with invasive bacteria is characterized by an accumulation of neutrophils in the lamina propria, and neutrophil transmigration to the luminal side of the crypts. Intestinal epithelial cells play an important role in the recruitment of inflammatory cells to the site of infection through the secretion of chemokines. However, little is known regarding the expression, by epithelial cells, of molecules that are involved in interactions between the epithelium and neutrophils following bacterial invasion. We report herein that expression of ICAM-1 on human colon epithelial cell lines, and on human enterocytes in an in vivo model system, is upregulated following infection with invasive bacteria. Increased ICAM-1 expression in the early period (4-9 h) after infection appeared to result mainly from a direct interaction between invaded bacteria and host epithelial cells since it co-localized to cells invaded by bacteria, and the release of soluble factors by epithelial cells played only a minor role in mediating increased ICAM-1 expression. Furthermore, ICAM-1 was expressed on the apical side of polarized intestinal epithelial cells, and increased expression was accompanied by increased neutrophil adhesion to these cells. ICAM-1 expression by intestinal epithelial cells following infection with invasive bacteria may function to maintain neutrophils that have transmigrated through the epithelium in close contact with the intestinal epithelium, thereby reducing further invasion of the mucosa by invading pathogens.

Gluten-sensitive enteropathy. Immunoglobulin G heavy-chain (Gm) allotypes and the immune response to wheat gliadin.

Anti-gliadin antibody was measured by radioimmunoassay in 30 Caucasians with gluten-sensitive enteropathy (GSE). 22 GSE patients maintained on a gluten-free diet for 1.5 to 20 yr (mean duration 76 mo) had elevated serum concentrations of IgG antigliadin antibody. Among GSE patients on a gluten-free diet, antigliadin antibody was seen only in those having the chromosome 14-encoded IgG immunoglobulin heavy chain allotype marker G2m(n). IgG antigliadin antibody was found in GSE patients with G2m(n) regardless of whether the HLA-B8 and/or -DR3 major histocompatibility complex antigens that occur frequently in GSE were present. No patient lacking G2m(n) had significant levels of antigliadin antibody. The association between antigliadin antibody and the immunoglobulin heavy chain allotype marker G2m(n) in GSE patients likely reflects the presence of Gmn-linked variable region genes or Gmn-linked genes that regulate variable region gene expression.

A distinct array of proinflammatory cytokines is expressed in human colon epithelial cells in response to bacterial invasion.

Pathogenic bacteria that penetrate the intestinal epithelial barrier stimulate an inflammatory response in the adjacent intestinal mucosa. The present studies asked whether colon epithelial cells can provide signals that are important for the initiation and amplification of an acute mucosal inflammatory response. Infection of monolayers of human colon epithelial cell lines (T84, HT29, Caco-2) with invasive strains of bacteria (Salmonella dublin, Shigella dysenteriae, Yersinia enterocolitica, Listeria monocytogenes, enteroinvasive Escherichia coli) resulted in the coordinate expression and upregulation of a specific array of four proinflammatory cytokines, IL-8, monocyte chemotactic protein-1, GM-CSF, and TNF alpha, as assessed by mRNA levels and cytokine secretion. Expression of the same cytokines was upregulated after TNF alpha or IL-1 stimulation of these cells. In contrast, cytokine gene expression was not altered after infection of colon epithelial cells with noninvasive bacteria or the noninvasive protozoan parasite, G. lamblia. Notably, none of the cell lines expressed mRNA for IL-2, IL-4, IL-5, IL-6, IL-12p40, IFN-gamma, or significant levels of IL-1 or IL-10 in response to the identical stimuli. The coordinate expression of IL-8, MCP-1, GM-CSF and TNF alpha appears to be a general property of human colon epithelial cells since an identical array of cytokines, as well as IL-6, also was expressed by freshly isolated human colon epithelial cells. Since the cytokines expressed in response to bacterial invasion or other proinflammatory agonists have a well documented role in chemotaxis and activation of inflammatory cells, colon epithelial cells appear to be programmed to provide a set of signals for the activation of the mucosal inflammatory response in the earliest phases after microbial invasion.

Apoptosis of human intestinal epithelial cells after bacterial invasion.

Epithelial cells that line the human intestinal mucosa are the initial site of host invasion by bacterial pathogens. The studies herein define apoptosis as a new category of intestinal epithelial cell response to bacterial infection. Human colon epithelial cells are shown to undergo apoptosis following infection with invasive enteric pathogens, such as Salmonella or enteroinvasive Escherichia coli. In contrast to the rapid onset of apoptosis seen after bacterial infection of mouse monocyte-macrophage cell lines, the commitment of human intestinal epithelial cell lines to undergo apoptosis is delayed for at least 6 h after bacterial infection, requires bacterial entry and replication, and the ensuing phenotypic expression of apoptosis is delayed for 12-18 h after bacterial entry. TNF-alpha and nitric oxide, which are produced as components of the intestinal epithelial cell proinflammatory program in the early period after bacterial invasion, play an important role in the later induction and regulation of the epithelial cell apoptotic program. Apoptosis in response to bacterial infection may function to delete infected and damaged epithelial cells and restore epithelial cell growth regulation and epithelial integrity that are altered during the course of enteric infection. The delay in onset of epithelial cell apoptosis after bacterial infection may be important both to the host and the invading pathogen since it provides sufficient time for epithelial cells to generate signals important for the activation of mucosal inflammation and concurrently allows invading bacteria time to adapt to the intracellular environment before invading deeper mucosal layers.

Secretion of proinflammatory cytokines by epithelial cells in response to Chlamydia infection suggests a central role for epithelial cells in chlamydial pathogenesis.

Chlamydia species infect epithelial cells at mucosal surfaces, and are major causes of sexually transmitted diseases. Infection is characterized by inflammation which is exacerbated upon reinfection, ultimately leading to tissue damage and scarring. Although central for the development of disease manifestations, little is known about the mechanisms that initiate and sustain the inflammatory response to Chlamydia. Infection of cervical and colonic epithelial cells with Chlamydia trachomatis and Chlamydia psittaci is shown in the present studies to upregulate mRNA expression and secretion of the proinflammatory cytokines IL-8, GRO alpha, GM-CSF, and IL-6. In contrast to the rapid, but transient, cytokine induction following infection with other invasive bacteria, the epithelial cytokine response to Chlamydia was delayed until 20-24 h after infection, persisted throughout the chlamydial growth cycle (2-4 d), and required bacterial protein synthesis. Moreover, epithelial cell lines and primary endocervical epithelial cells released IL-1alpha after Chlamydia infection, and increased secretion of the proinflammatory cytokines could be inhibited by anti-IL-1alpha. This suggests that IL-1alpha, released following lysis of infected epithelial cells, may amplify the inflammatory response by stimulating additional cytokine production by noninfected neighboring cells. These findings suggest a novel pathophysiologic concept wherein the acute host response to Chlamydia at mucosal surfaces is primarily initiated and sustained by epithelial cells, the first and major targets of chlamydial infection.

Role of intestinal epithelial cells in the host secretory response to infection by invasive bacteria. Bacterial entry induces epithelial prostaglandin h synthase-2 expression and prostaglandin E2 and F2alpha production.

Increased intestinal fluid secretion is a protective host response after enteric infection with invasive bacteria that is initiated within hours after infection, and is mediated by prostaglandin H synthase (PGHS) products in animal models of infection. Intestinal epithelial cells are the first host cells to become infected with invasive bacteria, which enter and pass through these cells to initiate mucosal, and ultimately systemic, infection. The present studies characterized the role of intestinal epithelial cells in the host secretory response after infection with invasive bacteria. Infection of cultured human intestinal epithelial cell lines with invasive bacteria, but not noninvasive bacteria, is shown to induce the expression of one of the rate-limiting enzymes for prostaglandin formation, PGHS-2, and the production of PGE2 and PGF2alpha. Furthermore, increased PGHS-2 expression was observed in intestinal epithelial cells in vivo after infection with invasive bacteria, using a human intestinal xenograft model in SCID mice. In support of the physiologic importance of epithelial PGHS-2 expression, supernatants from bacteria-infected intestinal epithelial cells were shown to increase chloride secretion in an in vitro model using polarized epithelial cells, and this activity was accounted for by PGE2. These studies define a novel autocrine/paracrine function of mediators produced by intestinal epithelial cells in the rapid induction of increased fluid secretion in response to intestinal infection with invasive bacteria.

Analysis of host responses to microbial infection using gene expression profiling.

Gene expression profiling offers new opportunities for understanding host-cell responses to microbial pathogens and their products. Current strategies involve either first identifying mRNAs that differ in their expression status under different experimental conditions and later defining the identity of the respective genes (for example, differential display or serial analysis of gene expression), or alternatively assessing changes in the expression of already defined genes (for example, cDNA or oligonucleotide microarrays). Early studies indicate the power of gene expression profiling for providing new insights into groups of genes whose expression is altered during the course of host-microbe interactions, and for the discovery of cellular genes that were not previously recognized to be regulated by infection.

Immune responses in human colon cancer. II. Cytotoxic antibody detected in patients' sera.

Complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), and spontaneous cell-mediated cytotoxicity (SCMC) were evaluated in patients with colon cancer with the use of a 51Cr release microcytotoxicity assay. We studied the sera and peripheral blood lymphocytes (PBL) from patients with colon cancer as well as from normal controls using three separate human colon cancer cell lines as targets. Antibody active in either the CDC or ADCC assay was detected in 11 of 14 (79%) patients with colon cancer, but none was found in 18 normal individuals. The ability of PBL from patients with colon cancer and from normal controls to mediate ADCC and SCMC did not differ significantly.