Background Although the BNT162b2 COVID-19 vaccine is known to induce IgG neutralizing antibodies in serum protecting against COVID-19, it has not been studied in detail whether it could generate specific immunity at mucosal sites, which represent the primary route of entry of SARS-CoV-2.Methods Samples of serum and saliva of 60 BNT162b2-vaccinated healthcare workers were collected at baseline, two weeks after the first dose and two weeks after the second dose. Anti-S1-protein IgG and IgA total antibodies titres and the presence of neutralizing antibodies against the Receptor Binding Domain in both serum and saliva were measured by quantitative and by competitive ELISA, respectively.Findings Complete vaccination cycle generates a high serum IgG antibody titre as a single dose in previously infected seropositive individuals. Serum IgA concentration reaches a plateau after a single dose in seropositive individuals and two vaccine doses in seronegative subjects. After the second dose IgA level was higher in seronegative than in seropositive subjects. In saliva, IgG level is almost two orders of magnitude lower than in serum, reaching the highest values after the second dose. IgA concentration remains low and increases significantly only in seropositive individuals after the second dose. Neutralizing antibody titres were much higher in serum than in saliva.Interpretation The mRNA BNT162b2 vaccination elicits a strong systemic immune response by drastically boosting neutralizing antibodies development in serum, but not in saliva, indicating that at least oral mucosal immunity is poorly activated by this vaccination protocol, thus failing in limiting virus acquisition upon its entry through this route.

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Purpose: We have shown previously that the MHC class II^negative murine TS/A adenocarcinoma is rejected in vivo if induced to express MHC class II molecules by transfection of the MHC class II transactivator CIITA. In this study, we explored the immunologic basis of tumor rejection and the correlation between histopathology of tumor tissue and immune rejection. Experimental Design: StableTS/A-CIITA transfectants were generated and injected into mice. In vivo cell depletion, immunohistochemistry of tumor tissues, and immune functional assays were done to assess the cellular and immunologic basis of rejection.

The HLA-DR or human Ia molecules are major histocompatibility complex (MHC)-encoded polymorphic cell surface glycoproteins made up of two noncovalently linked subunits of 34-36,000 (a) and 26-29,000 (fl) mol wt, respectively, which are believed to play an important role in the homeostasis of the immune system (reviewed in 1). Recent studies have shown that the human Ia molecular pool is composed of structurally distinct subsets of molecules. Some of these, like the NG1 and the NG2 subsets (2-4) are present in all individuals and constitute probably two isotypes of HLA-DR molecules. Some others of more restricted polymorphism, like DC-1 (5, 6), BR 4 × 7 (7), and I-LR1 (8) molecules, are present only in certain individuals and are believed to be coded for by genes in close linkage disequilibrium with the genes coding for the classic polymorphic HLA-DR molecules. The existence of structurally different families of Ia molecules raises the question of whether a given biological function may be related to a specific Ia subset.One of the approaches to study the relationship between structure and function is to generate cell variants that have lost the expression of the relevant structure and then to analyze whether the absence of such structure correlates with an alteration of a specific function. As a first step toward this goal we have isolated cell variants by immunoselection using either anti-NG1 or anti-NG2 monoclonal antibodies (Mab) and complement (C). This report describes the generation as well as the phenotypic characterization of HLA-DR-negative variants selected from the human B cell line Raji. Materials and MethodsMonoclonal antibodies. The following Mab were used in the present study: Dl-12 (anti-NG1) (2-4), BT 2.2 (anti-NG2) (4), BT 3/4 (anti-DC-1) (6), and W6.32 (anti-HLA-A, B, C common) (9).Selection procedure. Mutagenesis was performed as described by Kavathas et al. (10). Briefly, 5 × 106 Raji cells were irradiated with 300 rad and then cultured in 24-well Costar plates (Costar, Data Packaging~ Cambridge, MA) precoated with irradiated mouse macrophages, at a concentration of 1 × 10/ml. After 3-4 d the cells were immunoselected by adding a saturating dose of either D1-12 or BT-2.2 Mab and C. The addition of specific anti-Ia Mab and C was repeated every 4 d over a period of 1 mo. Cells surviving the treatment were cloned under limiting dilution conditions in the presence of irradiated mouse macrophages. Representative clones from three separate immunoselection experiments were chosen for further analysis.Flow microfluorometric analysis of stained cells. Cells were harvested from cultures in exponential phase of growth, washed twice with cold medium, and resuspended at a concentration of 5 × 106/ml. Cell suspension (0.1 ml) was incubated for 45 min at 4°C with 0.1 ml of a saturating J. ExP. MED.

Human interleukin-2 (IL-2) is a glycoprotein of relative molecular mass (Mr) 15,000, which is released by T lymphocytes on stimulation with antigen or mitogen and functions as a T-cell growth factor (TCGF) by inducing proliferation of activated T cells. It is generally accepted that resting or activated B cells do not respond directly to IL-2 but require for their proliferation other T-cell-derived lymphokines usually referred to as B-cell growth factors (BCGFs). Recently, however, a monoclonal antibody reacting with the IL-2 receptor molecules expressed by activated T cells (anti-Tac) was shown to react also with certain B tumour cells; in addition, murine B cells proliferate in response to pure human IL-2. We now show that recombinant IL-2, derived from Escherichia coli expressing the human gene, is able to promote strong proliferation of human B cells activated with protein-A-rich Staphylococcus aureus Cowans strain I. Moreover, we demonstrate that the anti-Tac antibody also reacts with S. aureus-activated normal B cells and inhibits sharply the proliferative response of such cells to IL-2. Finally, immunoprecipitation experiments reveal that anti-Tac defines similar molecules on activated T and B cells.