Expression of immunoglobulin isotypes by lymphoid cells of mouse intestinal lamina propria

Optimization of murine small intestine leukocyte isolation for global immune phenotype analysis

New efforts to understand complex interactions between diet, gut microbiota, and intestinal immunity emphasize the need for a standardized murine protocol that has been optimized for the isolation of lamina propria immune cells. In this study multiple mouse strains including BALB/c, 129S6/Sv/EvTac and ICR mice were utilized to develop an optimal protocol for global analysis of lamina propria leukocytes. Incubation temperature was found to significantly improve epithelial cell removal, while changes in media formulation had minor effects. Tissue weight was an effective method for normalization of solution volumes and incubation times. Collagenase digestion in combination with thermolysin was identified as the optimal method for release of leukocytes from tissues and global immunophenotyping, based on the criteria of minimizing marker cleavage, improving cell viability, and reagent cost. The effects of collagenase in combination with dispase or thermolysin on individual cell surface markers revealed diverse marker specific effects. Aggressive formulations cleaved CD8α, CD138, and B220 from the cell surface, and resulted in relatively higher expression levels of CD3, γδ TCR, CD5, DX5, Ly6C, CD11b, CD11c, MHC-II and CD45. Improved collagenase digestion significantly improved viability and reduced debris formation, eliminating the need for density gradient purification. Finally, we demonstrate that two different digestion protocols yield significant differences in detection of CD4(+) and CD8(+) T cells, NK cells, monocytes and interdigitating DC (iDC) populations, highlighting the importance and impact of cell collection protocols on assay outputs. The optimized protocol described herein will help assure the reproducibility and robustness of global assessment of lamina propria immune responses. Moreover, this technique may be applied to isolation of leukocytes from the entire gastrointestinal tract.

Isolation and purification of colon lamina propria dendritic cells from mice with colitis

Dendritic cells are prime antigen presenting cells for stimulation of T cell immune responses. These cells are present in trace amounts in normal tissue. At sites of disease the increased frequency of these cells interacting with T cells may provide the basis for the release of pro-inflammatory mediators and contribute to localised cell and tissue damage. Studies on dendritic cells in the colon lamina propria of inflammatory bowel disease (IBD) mice have been limited due to the difficulties encountered in the isolation and purification of sufficient numbers of these cells. This is the first detailed, reproducible method provided in the literature for the isolation of colon lamina propria dendritic cells from mice with colitis, yielding optimum purity of cells and sufficient numbers to advance the study of dendritic cell function in the colons of mice. The most frequently used identification marker of murine DC is the CD11c surface antigen. We have adapted, combined, and improved procedures developed for the isolation of other cell types, to develop an efficient procedure for the isolation of dendritic cells from colon tissue. This protocol describes a step-by-step method for optimising the purity and recovery of lamina propria CD11c+ dendritic cells from mice colons.

Importance of immunoglobulin E (IgE) in the protective mechanism against gastrointestinal nematode infection: looking at the intestinal mucosae

This review discusses experimental evidences that indicate the IgE participation on the effector mechanisms that leads to gastrointestinal nematode elimination. Data discussed here showed that, for most experimental models, the immune response involved in nematode elimination is regulated by Th-2 type cytokines (especially IL-4). However, the mechanism(s) that result in worm elimination is not clear and might be distinct in different nematode species. Parasite specific IgE production, especially the IgE produced by the intestinal mucosae or associated lymphoid organs could participate in the intestinal elimination of Trichinella spiralis from infected rats. Intestinal IgE may also be important to the protective mechanism developed against other gastrointestinal nematodes that penetrate the murine duodenum mucosa tissue, such as Strongyloides venezuelensis and Heligmosomoides polygyrus. At least in Trichinella spiralis infected rats, the results indicated that intestinal IgE might work independently from mast cell degranulation for worm elimination.

The B-cell system of human mucosae and exocrine glands

The mucosae and exocrine glands harbour the largest activated B-cell system of the body, amounting to some 80-90% of all immunoglobulin (Ig)-producing cells. The major product of these immunocytes is polymeric (p)IgA (mainly dimers) with associated J chain. Both pIgA and pentameric IgM contain a binding site for the polymeric Ig receptor (pIgR), or secretory component (SC), which is a requirement for their active external transport through secretory epithelia. The pIgR/SC binding site depends on covalent incorporation of the J chain into the quaternary structure of the polymers when they are produced by the local immunocytes. This important differentiation characteristic appears to be sufficient functional justification for the J chain to be expressed also by most B cells terminating at secretory effector sites with IgD or IgG production; they probably represent a "spin-off" from sequential downstream CH switching on its way to pIgA expression, thus apparently reflecting a maturational stage of effector B-cell clones compatible with homing to these sites. Observations in IgA-deficient individuals suggest that the magnitude of this homing is fairly well maintained even when the differentiation pathway to IgA is blocked. Certain microenvironmental elements such as specific cytokines and dendritic cells appear to be required for induction of IgA synthesis, but it remains virtually unknown why this isotype normally is such a dominating product of local immunocytes and why they have such a high level of J chain expression. Also, despite the recent identification of some important requirements in terms of adhesion molecules (e.g. integrin alpha 4 beta 7 and MAdCAM-1) that explain the "gut-seeking" properties of enterically induced B cells, the origin of regionalized homing of B cells to secretory effector sites outside the gut remains elusive. Moreover, little is known about immune regulation underlying the striking disparity of both the class (IgD, IgM) and subclass (IgA1, IgA2, IgG1, IgG2) production patterns shown by local immunocytes in various regions of the body, although the topical microbiota and other environmental stimuli might be important. Rational design of local vaccines will depend on better knowledge of both inductive and migratory properties of human mucosal B cells.

Lamina propria T cell subsets in the small and large intestine of euthymic and athymic mice

We investigated lamina propria T cells from the small intestine (jejunum/ileum) and the large intestine (colon) of euthymic (BALB/c, C.B-17, C57BL/6) and athymic (C57BL/6 nu/nu; BNX bg/bg nu/nu xid/xid) mice. CD3+ T cells represented about 40% of the lamina propria lymphocytes (LPL) from the small or the large intestine of euthymic mice, and 20-30% of the LPL populations from the small or large intestine of athymic mice. In the lamina propria T cell population of the small intestine, 85% were of the alpha beta lineage in euthymic mice, but only 40% were of the alpha beta lineage in athymic mice. T cells of the gamma delta lineage were thus more frequent than T cells of the alpha beta lineage in the intestinal lamina propria T cells of extrathymic origin. CD4+ T cells represented 40% of the lamina propria T cells in the small as well as in the large intestine of euthymic mice, and 20-30% of the T cells in the lamina propria of the nude mouse gut. In euthymic mice, 40% of the T cells in the small intestine lamina propria, and 30% of the T cells in the colonic lamina propria were CD8+. In intestinal lamina propria T cell populations of athymic mice, the CD8+ T cell population was expanded. Most (60-70%) CD8+ T cells in the lamina propria of the small and the large intestine of euthymic and athymic mice expressed the homodimeric CD8 alpha + beta- form of the CD8 coreceptor. A fraction of 15-20% of all CD3+ T cells in the lamina propria of the small and the large intestine of euthymic and athymic mice were 'double negative' CD4- CD8-. A large fraction of the TCR alpha beta + T cells in the colonic lamina propria (but not in the small intestine lamina propria) of euthymic mice expressed the CD2 and the CD28 costimulator molecules, the adhesion molecule LECAM-1 (CD62 L), and could be activated in vitro by CD3 ligation. These data reveal a considerable heterogeneity in the surface phenotype and the functional phenotype of murine lamina propria T cells.

Murine intestinal antibody response to heterologous rotavirus infection

Rotavirus is the most important worldwide cause of severe gastroenteritis. Extensive efforts have been devoted to the design of a vaccine that will prevent disease, but development of a more effective vaccine strategy may require progress in the understanding of the mucosal immune response to replicating viral antigens. In this article, we report the characterization of the intestinal antibody response of a murine model to heterologous infection with the rhesus rotavirus vaccine strain. We have adapted the enzyme-linked immunospot assay to measure this response without the difficulties associated with measurement of antibodies in intestinal contents or the artifacts associated with culturing of lymphocytes. The predominant response in terms of antibody-secreting cells (ASC) is seen in the small intestine lamina propria, which can be measured within 4 days of infection, peaks 3 weeks after infection, and remains near that level for longer than 8 weeks. The magnitude of the immunoglobulin A (IgA) cell response is approximately 10 times greater than the intestinal IgG cell response, and IgM cells are rare. Virus-specific ASC constitute approximately 50% of all ASC in the gut at the peak of the virus-specific response. This response is considerably greater than responses to nonreplicating mucosal antigens measured by similar techniques. Enteral infection engenders minimal virus-specific ASC response in the spleen. Rhesus rotavirus-specific enzyme-linked immunosorbent assay and neutralization assays of serum and intestinal contents did not correlate with virus-specific ASC response.

IgG in murine intestinal secretions. Aging effect and possible physiological role

To assess the role of, and age-associated alterations in, intraluminal IgG in the intestine, total IgG and subclass distribution in small intestinal perfusates and pilocarpine-stimulated intestinal secretions were measured under non-fasting conditions in three groups of BALB/c mice: 2-3, 12-14, and over 24 months old. Total intraluminal IgG and its subclasses (i.e. IgG1, IgG2a, and IgG2b) increased with age. However, the binding capacities of natural intraluminal IgG antibody (Ab) for outer membrane antigen (Ag) from normal habitant bacteria (Escherichia coli and Enterobacter agglomerans) were markedly reduced in the aged lavage samples as compared with such binding in samples from the other two age groups. The striking similarity to serum in the magnitude of the increase of intraluminal IgG and also in the distribution patterns of its subclasses in the small intestinal perfusates from all age groups suggests that the serum is a major source of the IgG. The intraluminal IgG may play some role in humoral immune protection under physiologic conditions of the gut lumen.

Improved procedure for the isolation of functionally active lymphoid cells from the murine intestine

An isolation procedure for functionally active lamina propria lymphoid cells (LPL) from the murine intestine is described. The procedure involved EDTA-dithiothreitol incubation of intestinal tissue to remove epithelial and intraepithelial cells, followed by collagenase digestion of the basement membrane to liberate part of the LPL. The LPL were suspended by squeezing the remaining tissue strips through a nylon gauze filter. Functional activity was tested by enumeration of the immunoglobulin-secreting cells in the cell suspensions obtained by an isotype-specific protein A plaque-forming cell assay. On average 1-2 X 10(8) LPL were isolated from the intestine of C3H/He mice. 11% of these cells actively secreted Ig. From these Ig-secreting cells 99% produced IgA. The isolation procedure described in this paper permitted a higher recovery of viable cells than has previously been obtained with other methods.

Lymphokine production by mitogen and antigen activated mouse intraepithelial lymphocytes

Although most intraepithelial lymphocytes (IEL) in mouse small intestine bear surface markers classically associated with T lymphocytes, the T-cell nature of these cells remains controversial. In the present study IEL from normal mice, or from mice infected with the gut nematode Trichinella spiralis, were therefore tested for their ability to produce T-cell-derived lymphokines in response to in vitro stimulation with concanavalin A (Con A) or with specific worm antigens. The data show that Con A-stimulated IEL produce minimal amounts of IL-2, and intermediate levels of IFN-gamma and IL-3 in comparison to the levels produced by spleen T cells. The FDC-P2 cell line, which proliferates in response to both IL-3 and GM-CSF, was identified as the most sensitive and reproducible indicator of lymphokine activity in supernatants from mitogen-stimulated IEL from normal mice. IEL isolated from mice infected with T. spiralis also produced high levels of FDC-P2 growth factors when challenged in vitro with Trichinella-derived antigens; however, normal IEL did not respond to this stimulus. The data thus provide evidence that antigen-sensitive T cells can arise in (or migrate to) the gut epithelium during gut infection.

A sensitive method for the detection of specific antibody production in different isotypes from single lamina propria plasma cells

A sensitive and reproducible method for the detection of specific antibody production (or total immunoglobulin secretion) at the single cell level from isolated lamina propria lymphocytes was developed. The cells were prepared from mouse intestinal mucosa by enzyme extraction with collagenase, and antibody secretion was demonstrated with a solid phase enzyme-linked immunospot (ELISPOT) assay. Oral immunizations with cholera toxin or keyhole limpet haemocyanin to mice gave high numbers of highly antigen-specific spot-forming cells (SFC) among isolated lamina propria lymphocytes. Spots were shown to result from active synthesis of immunoglobulin in vitro. The variation in SFC numbers between individual animals after a given protocol of oral immunizations was found to be 25% and between equal groups analysed on different occasions, 12%. Kinetics of primary as well as secondary immune responses after oral immunizations with cholera toxin were easily monitored. A single dose of cholera toxin gave rise to 230 antitoxin SFC/10(7) isolated lamina propria lymphocytes. Each additional dose stimulated to increasing numbers of specific SFC with roughly 7000 antitoxin SFC/10(7) cells after five immunizations. Monitoring of day-by-day responses after oral booster immunizations demonstrated peak SFC numbers on day 8 after antigen administration. The total number of immunoglobulin-secreting (Ig) cells and the isotype distribution of specific SFC could also be determined. In the peak antitoxin response, 8% of the isolated total Ig-secreting lamina propria cells were active against cholera toxin, and of these 80% were producing IgA. This method has also been successfully used in humans and rabbits to demonstrate specific antibody production by single lamina propria plasma cells.

Intestinal immunity and inflammation: recent progress

The previous sections illustrate that we are still defining (a) which sets of lymphoid cells are present in the intestine and which are not, (b) which sets are peculiar to the intestine, and (c) how the sets that are there function in the intestinal microenvironment. An understanding of the latter point is going to require knowledge of how these sets communicate with and regulate one another via cell surface molecules such as MHC class I and class II molecules, and via soluble mediators or lymphokines. The recent advances in various technologies make this a particularly exciting time in this field because the tools are now available to address and answer some of these basic and important questions in mucosal immunology. At the same time these advances hold great promise for our eventual understanding of chronic inflammatory diseases of the intestine. As was mentioned at the outset, the immune system has considerable power for both protection and destruction. It remains a puzzle how this latter potential is contained and controlled in the intestine of most individuals, such that they do not have inflammatory disease even in the setting of intense stimulation by substances, such as endotoxin, that are phlogistic elsewhere in the body. An answer to the question of why everyone does not have intestinal inflammation could provide new insights into the mechanisms involved in chronic intestinal inflammatory diseases. The recent advances just detailed, as well as others sure to come, suggest that it is only a matter of time before such questions are answered.

Cytoplasmic immunofluorescence and light scatter analysis of lamina propria plasma cells by flow cytometry

Cytoplasmic immunoglobulin of lamina propria plasma cells was analyzed by immunofluorescence on the flow cytometer. Lymphoid cells were made permeable to immunofluorescent reagents by treatment with Triton X-100. These cells were then reacted with FITC (green) anti-light chain and with phycoerythrin (red) anti-heavy chain antibodies. Flow cytometric analysis of these cells revealed that plasma cells expressing cytoplasmic immunoglobulin light and heavy chains were specifically stained by the immunofluorescent reagents. These plasma cells were also shown to have membrane Ig as detected by cell surface immunofluorescence. Light scatter analysis indicated that these plasma cells could be distinguished from lymphocytes by 90 degrees light scatter. These studies provide a method by which several parameters of gut plasma cells can be analyzed by flow cytometry.

Repopulation of the gut lamina propria with IgA-containing cells by lymphoid cells isolated from the gut lamina propria

Migration and lodging properties of IgA cells and their precursors of the gut lamina propria (GLP) were studied by transfer of highly purified GLP lymphoid cells between immunoglobulin allotype-congenic mice (CB-20 to BALB/c). The donor IgA-containing ( cIgA ) cells appeared in the GLP of the recipients at day 1, peaked at days 12-15 (late repopulation peak) and persisted up to day 20 after cell transfer. An additional peak at day 3 (early repopulation peak) was seen only when large numbers of GLP B cells were transferred. Few cIgA cells appearing in spleen and mesenteric lymph nodes were seen mainly at days 12-15. The early repopulation peak was probably formed by the differentiation and accumulation of IgA blasts, recirculating IgA-bearing cells and some IgA precursors. The former 2 cell types homed directly back, while the later homed indirectly via spleen to the GLP. The late repopulation peak was possibly formed by the homing and differentiation of Peyer's patch IgA precursors arriving in the GLP with membrane immunoglobulins unchanged. These GLP IgA precursors migrated first to the spleen and later back to the GLP, where they differentiated into IgA plasma cells.