[Changes in the membrane receptors of lymphocyte populations during immunization]

A population of splenic lymphocytes has been studied as well as their surface antibodies and their affinity for antigen in different days and periods of immunization. Fractionation of a specific population of lymphocytes having an affinity for antigens coated on glass beads were accomplished. The other aspecific population did not bind ot the glass beads and was not retained on the column. During the primary immuno-response the number of lymphocytic cells with surface antibodies specific for antigen was higher than in the booster response: in secondary response only the total number of antibody forming-cells increases while the number of lymphocytes with surface antibodies is constant. The authors suppose that the surface of spleen lymphocytes is modificated in different way at different time, by immunizing antigen.

Localization of polypeptides in frog virus 3 by radioiodination technique

Frog virus 3 is an amphibian icosahedral deoxyribovirus which replicates in the cytoplasm of infected cells. The radioiodination of purified virions using the enzyme lactoperoxidase has shown that the major component of the structural proteins is only partially exposed through the lipoprotein membrane that constitutes the outer layer of the icosahedral capsid.

Polypeptide analysis of a "Leishmania donovani" strain isolated during an outbreak of visceral leishmaniasis in northern Italy

The results of the analysis of the polypeptide composition of a strain of Leishmania donovani isolated during an outbreak of kala azar in northern Italy are reported.

Evidence for somatic generation of antibody diversity

RNA preparations containing 70-80% mouse kappa-chain mRNA have been prepared. The remainder consists of many RNA species, each of which represents a small fraction of the total RNA. The kappa-chain mRNA preparation hybridizes with mouse liver DNA with bi-phasic kinetics, indicating that it consists of two fractions -"unique" and "reiterated." Competition hybridization experiments show that the homology among the unique fractions from different mRNAs is the same as the homology among the amino acid sequences of the corresponding kappa-chains. Hence, in addition to the C-region (constant-region) sequences, (most of) the V-region (variable-region) sequences are also derived from unique germ line genes. The reiterated fractions from different kappa-chain mRNAs show essentially complete homology with each other. This fraction seems to consist mostly of sequences which do not code for amino-acid sequences of the secreted polypeptide chain, i.e., the "external" section of the mRNA molecule. It is concluded that the number of germ line genes is too small to account for the observed diversity of antibody molecules.

Induction of antibody synthesis. Effect of blocking defined determinants of an antigen

Rabbit antibody specific for bovine γ-globulin (BGG) and for the dinitrophenyl group (DNP) was used to block defined determinants of BGG—DNP, and the immunogenicity of antibody-complexed BGG—DNP in rabbits was compared with that of BGG—DNP. Antibody-complexed BGG—DNP was less immunogenic, eliciting less antibody reactive with BGG—DNP. However, BGG-specific antibody, in contrast to DNP-specific antibody, suppressed primarily the induction of antibody specific for the BGG determinants of BGG—DNP. This finding suggests: (1) that induction of antibody specific for a given determinant of an antigen requires the active participation of that determinant as an inducer, and (2) that the immunosuppressive action of antibody is determinant-specific and not antigen-specific. The immunogenicity of antibody-complexed sheep erythrocytes was also studied in mice. Rabbit antibody to sheep erythrocytes, in different amounts, was used to block determinants on the surface of sheep erythrocytes. The agglutinin response was inversely proportional to the amount of antibody used to complex the erythrocytes. This finding supports the role of determinants as inducers of antibody formation and indicates that the immunogenicity of an antigen is a function of the number of determinants it carries in an accessible reactive state.