Inhibition of cluster formation and lymphocyte proliferation by anti-fibronectin antiserum

Focussing human B cell specificity by immunoselection via antigen-presenting cells in vitro

We present a protocol for in vitro immunization of B cells using monocyte-derived accessory cells (MoAC). MoAC are developed from human peripheral blood monocytes in culture and represent functionally competent inducers of antigen-specific immune responses. Using MoAC, we attempted to immunoselect TT-specific lymphocytes by rosetting. Adherent human MoAC were pulsed with tetanus toxoid (TT) and allowed to form clusters with autologous lymphocytes, followed by removal of non-adherent cells. After one week of culture, a specific anti-TT antibody response emerged on a low background of unspecific Ig. In comparison, cultures which had not been selected for adherent cells produced a high polyclonal background. Our results demonstrate that from peripheral blood cells, previously not a favourable source for in vitro immunization, in a majority of tests antigen-specific B cells could efficiently be immunoselected via adherence to autologous antigen-presenting cells, leading to a high-titre in vitro immunization.

Microvascular basal lamina antigens disappear during cerebral ischemia and reperfusion

BACKGROUND AND PURPOSE

Changes in vascular permeability are well-known and important consequences of cerebral ischemia. The development of edema and of petechial hemorrhage is connected to altered vascular integrity. A major part in microvascular integrity is played by the basal lamina.

METHODS

The fates of the basal lamina components laminin, fibronectin, and type IV collagen during middle cerebral artery occlusion (2 hours, n = 3) and occlusion (3 hours) with reperfusion (1 hour, n = 3; 4 hours, n = 3; and 24 hours, n = 4) were evaluated in the nonhuman primate. Specific monoclonal antibodies against these components were used. The number and size distribution of the microvessels in each specimen were determined by video-imaging microscopy, and the relative fluorescence intensity of laminin was semiquantified by laser confocal microscopy. Basal lamina antigen presentations were compared by double-stain immunofluorescence histochemistry.

RESULTS

The number of microvascular structures defined by the presence of each basal lamina antigen decreased significantly up to 24 hours of reperfusion (P < .0001). The ratio of laminin-containing vessels between the ischemic and nonischemic territories decreased significantly from control (0.98 +/- 0.04) to 2 hours of ischemia (0.83 +/- 0.09) and 1 hour (0.79 +/- 0.08), 4 hours (0.77 +/- 0.06), and 24 hours of reperfusion (0.55 +/- 0.07). The ratio of fibronectin (cellular) and of collagen (IV)-containing vessels decreased from 0.98 +/- 0.04 to 0.75 +/- 0.1 and from 1.02 +/- 0.03 to 0.57 +/- 0.1, respectively. Mean laminin fluorescence intensity decreased from 76.1 +/- 6.0 U (controls) to 52.0 +/- 14.6 U (24 hours of reperfusion; P < .001).

CONCLUSIONS

The significant parallel losses of three basal lamina components, both in number and intensity, contribute to loss of microvascular integrity. These phenomena may be important for understanding cell extravasation and the hemorrhagic consequences of acute stroke.

Cytokines and adherence molecules involved in spontaneous dendritic cell-lymphocyte clustering in skin afferent lymph

The skin afferent lymph dendritic cell (DC) spontaneously forms clusters with autologous T cells. The role of adhesion molecules and cytokines in this process was investigated. Analysis of the expression of adhesion receptors on the canine peripheral lymph DC revealed the presence of CD54, CD58, CD18 as well as CD49d and CD49e molecules and cell surface fibronectin. The CD54 and CD58 molecules were found to play a key role in the 'spontaneous' lymph cell clustering. Antibody against fibronectin, a substrate for CD49d and CD49e receptors, reduced DC-lymphocyte binding. Analysis of the effect of cytokines revealed that the pro-inflammatory IL1 beta rather than IL1 alpha, and TNF alpha may be responsible for the enhanced lymph cell in vitro clustering. The IL6 had no such augmenting effect. The enhancing effect of endogenous IL1 beta present in lymph was reduced by the IL1 beta neutralizing antibody. The effect of exogenously added IL1 beta was also limited by the IL1 receptor antagonist. The IL1Ra alone had no effect on cell binding, even when used in the high doses. Neutralizing of IL1Ra in lymph with the specific antibody brought about augmented cluster formation. The enhancing properties of TNF alpha on cell binding were reduced by the TNF alpha neutralizing antibody. The IL10 significantly limited lymph DC cluster formation with T cells. In conclusion, these data demonstrate that the present in lymph IL1 beta and TNF alpha may be responsible for the observed in vitro enhanced cluster formation of lymph DC with autologous T lymphocytes. Cell binding can be reduced by IL1Ra and by IL10. It provides insight into the potential clinical use of these inhibitors.

Interaction of fibronectin and fibronectin binding protein (FnBP) of Staphylococcus aureus with murine phagocytes and lymphocytes

In the present study we examined the in vitro and in vivo interactions of a cloned staphylococcal fibronectin binding protein (FnBP) and plasma fibronectin (Fn) with polymorphonuclear cells (PMNs) and macrophages, and how antibodies against FnBP affect the phagocytosis process in vitro. Moreover, the interaction of FnBP and Fn coupled on latex beads as 'artificial bacteria' and 'artificially opsonized bacteria' with murine spleen cells and peritoneal macrophages was tested. The major finding of the present study is that antibodies against the FnBP of Staphylococcus aureus (S. aureus) and low concentration of antibodies recognized two IgG-binding domains of protein A (SpA) are effective in the promotion of phagocytosis in vitro. It was also observed that FnBP has a chemoattractant activity and causes accumulation of PMNs and macrophages in the mouse peritoneal cavity when injected 24 h before irritation of peritoneal exudate. It seems likely that this activity is connected with binding to Fn molecules since formalin inactivation of FnBP (60%) abolished it. In the in vitro phagocytosis assay in the presence of FnBP (in a medium supplemented with serum depleted of Fn), ingestion of bacteria by phagocytes was identical to assay carried out in the presence of BSA. However, addition of plasma fibronectin caused an increased uptake of bacteria by macrophages and to a lesser degree by PMNs. We observed that in a population of normal splenocytes, those cells that effectively bound FnBP- and Fn-coated latex beads were mostly those cells exhibiting macrophage and dendritic morphology. In populations of spleen cells of animal infected with S. aureus, T lymphocytes were also found to bind FnBP- and Fn-coated latex beads. These data suggest that FnBP may have the ability to promote aggregation of immune cells, either directly or by interaction with plasma Fn, which can be helpful in certain cell-cell interactions taking place at the initial stages of specific immune response.

Interaction of staphylococcal fibronectin binding protein (FnBP), TSST-1 and alpha-toxin with murine lymphocytes

The most restrictive factor in the inductive phase of immune response is the contact and adhesion of antigen-presenting cells and responding lymphocytes. We report the in vitro formation of aggregates (clusters) of murine T lymphocytes and dendritic cells (DC) pulsed with highly purified staphylococcal toxins (TSST-1, alpha-toxin) and gene-cloned surface fibronectin binding protein (gal-FnBP). A high percentage of T lymphocytes were involved in clustering with TSST-1-pulsed DC. Lymphocytes of mice infected with Staphylococcus aureus (strain Cowan 1) 21 days before testing, clustered with the same ability as cells of mice infected 3 days before. Dendritic cells pulsed with alpha-toxin formed a moderate number of clusters only when co-cultured with T lymphocytes of mice infected 3 days before the test. FnBP-pulsed DC aggregated strongly with T lymphocytes. This response peaked at 3-4.5 h-cultures and increased again after 24 h. We concluded that at the beginning of co-culture, FnBP amplified the cells' adhesion process on antigen-independent way. This conclusion is supported by the observation that DC pulsed with formalin-modified FnBP (with a 65% decreased ability to bind fibronectin) formed fewer clusters with T-immune cells than dendritic cells pulsed with native, non-treated FnBP.