A gene region encoding a segment of the major surface protein, HBsAg, of hepatitis B virus was analyzed from serum samples after orthotopic liver transplantation of three hepatitis B virus chronic carrier patients treated with a human anti-hepatitis B virus monoclonal antibody (SDZ OST 577). Each of these three patients became HBsAg negative after transplantation and therapy with the human anti-hepatitis B virus monoclonal antibody but returned to HBsAg positivity (first detected 143,251 and 252 days after the transplantation). Polymerase chain reaction DNA amplification was performed on DNA from serum samples showing low levels of recurrent HBsAg and reduced antigen reactivity with SDZ OST 577 antibody. Polymerase chain reaction DNA included a 230-bp highly conserved, major S gene region that was cloned into M13 bacteriophage; analysis of this DNA segment provided a consensus of DNA sequences for the serum samples exhibiting altered reactivity with the therapeutic monoclonal. Analysis of independent DNA clones from serum samples of patients exhibiting low but detectable recurrent serum levels of posttherapy HBsAg revealed the presence of S protein variant sequences when compared with polymerase chain reaction DNA derived from the original infected liver or pretherapy serum HBsAg. Genetic variation was predominant in a highly conserved peptide domain that has previously been implicated in antibody binding and neutralizing antibody epitopes. In independent patients infected with either adw or ayw hepatitis B virus subtypes, single nucleotide changes resulted in one to two amino acid differences for each variant allele (residues 124, 129, 131, 137, 140 and/or 145) when compared with pretherapy viral DNA. Administration of serum containing one of these variant viruses to a single hepatitis B-naive chimpanzee resulted in subclinical hepatitis and detectable levels of circulating anti-HBs and anti-HBc antibodies 49 and 70 days after virus administration, respectively. Hepatitis B virus DNA was recovered on liver biopsy between 6 and 8 wk after inoculation, although the animal remained persistently seronegative for HBsAg. DNA sequence analysis of both primate and patient liver hepatitis B virus confirmed the presence of the DNA encoding the S protein variant and associates this DNA with the predominant hepatotropic virus in liver infection.

A rat cell line (A2T2C4) transformed with adenovirus type 2 elicited cytotoxic T Iymphocytes in syngeneic rats. Cytotoxicity was abolished by a rabbit antiserum directed against the major histocompatibility (AgB) antigens and by a syngeneic rat antiserum raised against the virus-transformed cellline. The syngeneic antiserum immunoprecipitated surface proteins with apparent molecular weights of 45,000 19,000, 17,000, and 12,000 from the A2T2C4 cells but it displayed no reactivity against primary rat fibroblasts and spleen cells. The rabbit antiserum against AgB antigens precipitated a 19,000-dalton component from the A2T2C4 cells which was not observed in primary rat fibroblasts. Sequential immunoprecipitation revealed identity between the major polypeptides recognized by the two antisera. Because the rabbit anti-AgB antigen serum was specific for the transplantation antigen subunits and because the syngeneic rat antiserum against the A2T2C4 cells failed to react with the AgB antigens in normal cells, it is concluded that the 19,000-dalton component is coprecipitated with the A&B antigens. Antisera directed specifically against #2-microglobulin and the alloantigenic AgB antigen subunit also coprecipitated the 19,000-dalton component.

The major human and murine histocompatibility antigens are tetrameric molecules with an apparent molecular weight of about 130,000. They are composed of two types of polypeptide chains. The two light chains, previously identified as 6B2-microglobulins, are bound to the two heavy, alloantigenic HL-A or H-2 polypeptide chains by noncovalent interactions only. The heavy chains are held together by disulfide bridge(s) located in the part of the molecule that is attached to the cell membrane.By limited proteolysis of the histocompatibility antigens evidence was obtained suggesting that the heavy chain may consist of three compact domains connected by more extended stretches of polypeptide chain. Each domain appeared to contain a single disulfide bridge encompassing about 60 to 70 amino-acid residues.Staphylococcus aureus protein A is known to bind exclusively to the Fc region of immunoglobulin G. It was, however, observed that protein A interacts in a similar way with the H-2 antigen heavy chain. This observation, together with the homology of the primary structure of ,62-microglobulin to immunoglobulin G, the tetrameric structure of the alloantigens, the organization of the heavy polypeptide chain into compact domains, and the presence of a single, immunoglobulin-like disulfide loop in each domain, establishes a close similarity in structure between histocompatibility antigens and immunoglobulins. The similarity in structural features suggests a common evolutionary origin of the two types of molecules.

Subclasses of lymphocytes can be separated on gradients of non-toxic polyvinylpyrrolidone-coated colloidal silica (Percoll) by virtue of differential densities. Such gradients can yield functionally active lymphocyte populations after brief centrifugation. Gradients can be generated in a discontinuous step fashion and centrifuged in standard table-top laboratory centrifuges or as self-generating gradients during ultracentrifugation. The density medium has low viscosity and can be made isotonic for virtually any use. Gradients have proved useful in both human and experimental animal studies, and high percentage yields allow for separations from small cell numbers. Methods are described for separation of whole blood and lymphoid subpopuctions. The cytoxic capability of various density fractions was evaluated for mixed lymphocyte culture-induced allogeneic killing and spontaneous, so-called "natural" killer cell activity. The lower density associated with blast transformation allows for significant enrichments of stimulated cells from in vitro cultures. Higher thymidine incorporation, restimualtion in mixed lymphocyte reactions, and greater cytotoxic capacity are associated with these "blast" fractions.

Antigenic domain 1 (AD-1) on glycoprotein gp58 of human cytomegalovirus was characterized in detail, using mouse and human monoclonal antibodies as well as human convalescent sera. Series of procaryotically * Corresponding author.