Peripheral blood lymphocytes immunophenotype and serum concentration of soluble HLA class I in burn patients.

The level of the soluble form of histocompatibility class I antigens, associated with beta(2)-microglobulin (sHLA-I) has been determined by an ELISA sandwich method in serum from burned patients (n=42) and healthy volunteers (n=30). The sHLA-I level was insignificantly increased in burn patients at the stage of burn shock (1284+/-324U/ml, mean+/-S.E.M.) and after day 28 postburn (1368+/-258U/ml) compared to volunteers (1150+/-90U/ml). At the same time a decrease of sHLA-I levels between 4 and 14 days (638+/-178U/ml) was determined (P<0.05). Increased levels of sHLA, though not significant, were detected in patients with TBSAB >70% in comparison to patients with TBSAB from 30 to 70% during burn shock (1493+/-528 and 1075+/-339U/ml, respectively). Expression of membranous HLA class I antigens (mHLA-I) in peripheral blood lymphocytes (PBLs) was assayed simultaneously by indirect immunofluorescence. The number of CD3(+), CD4(+), CD8(+), CD25(+), CD71(+) and CD26(+) lymphocytes was also evaluated. The expression of mHLA-I in PBLs was increased significantly in patients with TBSAB <70% at early postburn period. Daily monitoring showed that the relative numbers of CD25(+) and CD71(+) lymphocytes in patients varied greatly within short intervals of time during burn shock. The data obtained suggest that mHLA-I expression can reflect postburn lymphocyte activation. The serum content of sHLA-I does not depend on lymphocyte number or activated lymphocyte number in peripheral blood at burned patients.

Binding of HIV-1 to RBCs involves the Duffy antigen receptors for chemokines (DARC).

The Duffy Antigen Receptor for Chemokines (DARC) belongs to a family of erythrocyte chemokine receptors that bind C-X-C and C-C chemokines such as interleukin 8 (IL-8), monocyte chemoattractant protein 1 (MCP-1) and regulated-on-activation, normal T cell-expressed and -secreted (RANTES), but not macrophage inflammatory protein 1 alpha (MIP-1 alpha) or MIP-1 beta. DARC has also been identified to a receptor for malaria parasites Plasmodium vivax and Plasmodium knowlesi. In the present study, we show that HIV-1 binds to RBCs from Caucasian individuals via DARC making RBCs able to transmit HIV to peripheral blood mononuclear cells (PBMCs). Furthermore, binding of HIV-1 particles to RBCs is inhibited by treating these cells with recombinant RANTES, but not with recombinant MIP-1 alpha prior to their incubation with HIV-1. This finding suggests that RBCs may function as a reservoir for HIV-1 or as a receptor for the entry of HIV-1 into CD4-cell subsets as well as neurons or endothelial cells.

Erythrocyte receptors for Mycoplasma pneumoniae are sialylated oligosaccharides of Ii antigen type.

Among the pathological effects in man following infection with Mycoplasma pneumoniae is a transient autoimmune disorder characterized by the presence of high-titre erythrocyte autoantibodies (cold agglutinins). These autoantibodies are usually directed against the carbohydrate antigen termed I (ref. 3) which consists of a branched oligosaccharide. The mechanism by which the anti-I antibodies are elicited is unknown. However, sialic acid-containing receptors have been implicated in the adherence of M. pneumoniae to erythrocytes and other cell types, and both I and the related antigen i occur on erythrocytes in sialylated form: i is the predominant antigen on fetal erythrocytes and I is predominant in adults. Anti-I antibodies might arise in M. pneumoniae infection in response to a modification of the 'self' antigen-I as a result of its interaction with this agent. Here we report our study of the specificity of the interaction of M. pneumoniae with human erythrocytes. We found that this interaction is mediated by long chain oligosaccharides of sialic acid joined by alpha 2-3 linkage to the terminal galactose residues of poly-N-acetyllactosamine sequences of Ii antigen type.